Method and apparatus for control channel reception in wireless communication systems

ABSTRACT

The disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. The disclosure discloses a signaling method and apparatus for properly increasing a control channel detection complexity of a terminal in order to efficiently detect a control channel for performing coordinated transmission such as non-coherent joint transmission (NC-JT).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application Nos. 10-2019-0032969 and 10-2019-0073142filed on Mar. 22, 2019 and Jun. 19, 2019, respectively, in the KoreanIntellectual Property Office, the disclosures of which are hereinincorporated by reference in their entireties.

BACKGROUND 1. Field

The disclosure relates to a method and an apparatus for transmitting andreceiving a downlink control channel in a wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), Full Dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud Radio Access Networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,Coordinated Multi-Points (CoMP), reception-end interference cancellationand the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) andsliding window superposition coding (SWSC) as an advanced codingmodulation (ACM), and filter bank multi carrier (FBMC), non-orthogonalmultiple access (NOMA), and sparse code multiple access (SCMA) as anadvanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

In an LTE or NR system, a terminal performs blind decoding to receive acontrol channel (e.g., physical downlink control channel (PDCCH).Further, coordinated transmission may be performed for an efficienttraffic transmission.

SUMMARY

The disclosure provides signaling methods for properly increasing acontrol channel detection complexity of a terminal to match coordinatedcommunication transmission conditions.

The present disclosure has been made to address the above-mentionedproblems and disadvantages, and to provide at least the advantagesdescribed below.

In accordance with an aspect of the present disclosure, A methodperformed by a terminal in a communication system is provided. Themethod includes identifying a first number of cells corresponding to acapability to monitor physical downlink control channel (PDCCH)candidates based on a control resource set (CORESET) group identifierconfigured to each cell; determining a maximum number of PDCCHcandidates based on the first number of cells; identifying search spacesto monitor based on the maximum number of PDCCH candidates; andmonitoring a PDCCH on the identified search space.

In accordance with another aspect of the present disclosure, a methodperformed by a base station in a communication system is provided. Themethod includes identifying a first number of cells corresponding to acapability to monitor physical downlink control channel (PDCCH)candidates of a terminal based on a control resource set (CORESET) groupidentifier configured to each cell; determining a maximum number ofPDCCH candidates based on the first number of cells; identifying searchspaces to be monitored by the terminal based on the maximum number ofPDCCH candidates; and transmitting downlink control information on theidentified search space of a PDCCH.

In accordance with another aspect of the present disclosure, a terminalin a communication system is provided. The terminal includes atransceiver and a controller coupled with the transceiver and configuredto identify a first number of cells corresponding to a capability tomonitor physical downlink control channel (PDCCH) candidates based on acontrol resource set (CORESET) group identifier configured to each cell,determine a maximum number of PDCCH candidates based on the first numberof cells, identify search spaces to monitor based on the maximum numberof PDCCH candidates, and perform monitoring a PDCCH on the identifiedsearch space.

In accordance with another aspect of the present disclosure, a basestation in a communication system is provided. The base station includesa transceiver and a controller coupled with the transceiver andconfigured to identify a first number of cells corresponding to acapability to monitor physical downlink control channel (PDCCH)candidates of a terminal based on a control resource set (CORESET) groupidentifier configured to each cell, determine a maximum number of PDCCHcandidates based on the first number of cells, identify search spaces tobe monitored by the terminal based on the maximum number of PDCCHcandidates, and transmit downlink control information on the identifiedsearch space of a PDCCH.

Through a method for determining restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs proposed in thedisclosure, transmission and reception of PDCCHs can be performed moreefficiently in an environment in which coordinated communicationtransmission, such as NC-JT, and a CA are simultaneously supported, andthus scheduling flexibility can be heightened.

Effects that can be obtained in the disclosure are not limited to theabove-described effects, and other unmentioned effects can be clearlyunderstood by those of ordinary skill in the art to which the disclosurepertains from the following description.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainembodiments of the disclosure will be more apparent from the followingdetailed description, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a diagram of the basic structure of a time-frequencydomain in 5G.

FIG. 2 illustrates a diagram of frame, subframe, and slot structures in5G.

FIG. 3 illustrates a diagram of an example of bandwidth partconfiguration in 5G.

FIG. 4 illustrates a diagram of an example of a control resource setconfiguration of a downlink control channel in 5G.

FIG. 5 illustrates a diagram of the structure of a downlink controlchannel in 5G.

FIG. 6 illustrates a diagram of an example of a method for determining arestriction on the maximum number of PDCCH candidates in 5G.

FIG. 7 illustrates a diagram of another example of a method fordetermining a restriction on the maximum number of PDCCH candidates in5G.

FIG. 8 illustrates a diagram of radio protocol structures of a basestation and a terminal during performing of single cell, carrieraggregation, and dual connectivity according to an embodiment of thedisclosure.

FIG. 9A illustrates a diagram of a joint transmission (JT) techniqueaccording to an embodiment of the disclosure.

FIG. 9B illustrates a diagram of examples of radio resource assignmentper TRP in accordance with situations.

FIG. 10 illustrates a diagram of an example of a control channelconfiguration for coordinated communication transmission according to anembodiment of the disclosure.

FIG. 11 illustrates a diagram of an example of a method for managingrestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs according to an embodiment of the disclosure.

FIG. 12 illustrates a diagram of an example of control channelmultiplexing for coordinated communication transmission according to anembodiment of the disclosure.

FIG. 13 illustrates a diagram of a block diagram illustrating anoperation of a terminal for determining restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs according tosome embodiments of the disclosure.

FIG. 14 illustrates a block diagram of the internal structure of aterminal according to an embodiment of the disclosure.

FIG. 15 illustrates a diagram of the internal structure of a basestation according to an embodiment of the disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 15, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

Hereinafter, embodiments of the disclosure will be described in detailwith reference to the accompanying drawings.

In explaining the embodiments, explanation of technical contents thatare well known in the art to which the disclosure pertains and are notdirectly related to the disclosure will be omitted. This is to transferthe subject matter of the disclosure more clearly without obscuring thesame through omission of unnecessary explanations.

For the same reason, in the accompanying drawings, sizes and relativesizes of some constituent elements may be exaggerated, omitted, orbriefly illustrated. Further, sizes of the respective constituentelements do not completely reflect the actual sizes thereof. In thedrawings, the same drawing reference numerals are used for the same orcorresponding elements across various figures.

The aspects and features of the disclosure and methods for achieving theaspects and features will be apparent by referring to the embodiments tobe described in detail with reference to the accompanying drawings.However, the disclosure is not limited to the embodiments disclosedhereinafter, and it can be implemented in diverse forms. The mattersdefined in the description, such as the detailed construction andelements, are only specific details provided to assist those of ordinaryskill in the art in a comprehensive understanding of the disclosure, andthe disclosure is only defined within the scope of the appended claims.In the entire description of the disclosure, the same drawing referencenumerals are used for the same elements across various figures.

In this case, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions can be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions specified in the flowchart block or blocks.These computer program instructions may also be stored in a computerusable or computer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstruction means that implement the function specified in the flowchartblock or blocks. The computer program instructions may also be loadedonto a computer or other programmable data processing apparatus to causea series of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

Also, each block of the flowchart illustrations may represent a module,segment, or portion of code, which includes one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

In this case, the term “unit”, as used in an embodiment, means, but isnot limited to, a software or hardware component, such as fieldprogrammable gate array (FPGA) or application specific integratedcircuit (ASIC), which performs certain tasks. However, “unit” is notmeant to be limited to software or hardware. The term “unit” mayadvantageously be configured to reside on the addressable storage mediumand configured to execute on one or more processors. Thus, “unit” mayinclude, by way of example, components, such as software components,object-oriented software components, class components and taskcomponents, processes, functions, attributes, procedures, subroutines,segments of program code, drivers, firmware, microcode, circuitry, data,databases, data structures, tables, arrays, and variables. Thefunctionality provided for in the components and “units” may be combinedinto fewer components and “units” or further separated into additionalcomponents and “units”. Further, the components and “units” may beimplemented to operate one or more CPUs in a device or a securitymultimedia card. Further, in some embodiments, “unit” may include one ormore processors.

Hereinafter, the operational principle of the disclosure will bedescribed in detail with reference to the accompanying drawings. Indescribing the disclosure, a detailed description of related knownfunctions or configurations will be omitted if it is determined that itobscures the disclosure in unnecessary detail. Further, terms to bedescribed later are terms defined in consideration of their functions inthe disclosure, but may differ depending on intentions of a user or anoperator, or customs. Accordingly, they should be defined on the basisof the contents of the whole description of the disclosure.

Hereinafter, embodiments of the disclosure will be described in detailwith reference to the accompanying drawings. Although embodiments of thedisclosure are described hereinafter in a state where a 5G system isexemplified, the embodiments of the disclosure can also be applied evento other communication systems having similar technical backgrounds orchannel types. For example, LTE or LTE-A mobile communication and mobilecommunication technology being developed after 5G may be includedtherein. Accordingly, the embodiments of the disclosure can also beapplied to other communication systems through partial modificationsthereof within a range that does not greatly deviate from the scope ofthe disclosure by the judgment of those skilled in the art.

Further, in describing the disclosure, a detailed description of relatedfunctions or configurations will be omitted if it is determined that itobscures the disclosure in unnecessary detail. Further, terms to bedescribed later are terms defined in consideration of their functions inthe disclosure, but may differ depending on intentions of a user or anoperator, or customs. Accordingly, they should be defined on the basisof the contents of the whole description of the disclosure.

A wireless communication system was initially developed for the purposeof providing a voice-oriented service, but it has been expanded to, forexample, a broadband wireless communication system that provides ahigh-speed and high-quality packet data service like the communicationstandards, such as 3GPP high speed packet access (HSPA), long termevolution (LTE) or evolved universal terrestrial radio access (E-UTRA),LTE-Advanced (LTE-A), 3GPP2 high rate packet data (HRPD), ultra-mobilebroadband (UMB), and IEEE 802.16e.

In an LTE system that is a representative example of broadband wirelesscommunication systems, a downlink (DL) adopts an orthogonal frequencydivision multiplexing (OFDM) scheme, and an uplink (UL) adopts singlecarrier frequency division multiple access (SC-FDMA) scheme. The uplinkmeans a radio link in which a terminal (or user equipment (UE)) or amobile station (MS) transmits data or a control signal to a base station(BS) (or eNode B), and the downlink means a radio link in which the basestation transmits data or a control signal to the terminal. According tothe above-described multiple access schemes, data of respective users orcontrol information can be discriminated from each other by assigningand operating time-frequency resources for carrying the data or thecontrol information so as to prevent the time-frequency resources fromoverlapping each other, that is, to establish orthogonality.

As the post LTE communication system, the 5G communication system shouldsupport services that simultaneously satisfy various requirements ofusers and service providers because the 5G communication system isrequired to freely reflect the various requirements. Services beingconsidered for the 5G communication system may include enhanced mobilebroadband (eMBB), massive machine type communication (mMTC), andultra-reliability low-latency communication (URLLC).

The eMBB aims to provide a more improved data rate than the data ratesupported by the existing LTE, LTE-A, or LTE-Pro. For example, in the 5Gcommunication system, from the viewpoint of one base station, the eMBBshould provide the peak data rate of 20 Gbps in the downlink and thepeak data rate of 10 Gbps in the uplink. Further, the 5G communicationsystem should provide the peak data rate and an increased user perceiveddata rate of the terminal. To satisfy such requirements, it is requiredto improve various transmission/reception technologies including moreimproved multi input multi output (MIMO) transmission technology.Further, the current LTE transmits signals using the maximum 20 MHztransmission bandwidth in the 2 GHz band, whereas the 5G communicationsystem uses a wider frequency bandwidth than 20 MHz in the frequencyband of 3 to 6 GHz or 6 GHz or more, and thus can satisfy the data raterequired in the 5G communication system.

At the same time, the mMTC is under consideration to support applicationservices, such as the Internet of things (IoT), in the 5G communicationsystem. In order to efficiently provide the Internet of things, the mMTCrequires massive terminal connection support in a cell, terminalcoverage improvement, improved battery time, and terminal costreduction. Because the Internet of things is attached to various kindsof sensors and devices to provide communication functions, it shouldsupport a large number of terminals (e.g., 1,000,000 terminals/km′) inthe cell. Further, because there is a high possibility that the terminalsupporting the mMTC is located in a shaded area that the cell is unableto cover, such as underground of a building, due to the servicecharacteristics, a wider coverage is required as compared with otherservices provided in the 5G communication system. The terminalsupporting the mMTC should be inexpensive, and requires very longbattery lifetime, such as 10 to 15 years, because it is difficult tofrequently replace the battery of the terminal.

Last, the URLLC is a cellular based wireless communication service usedfor a specific purpose (mission-critical). For example, services usedfor remote control of a robot or machinery, industrial automation,unmanned aerial vehicle, remote health care, and emergency alert may beconsidered. Accordingly, it is required for the communication providedby the URLLC to provide very low latency and very high reliability. Forexample, a service supporting the URLLC should satisfy air interfacelatency that is shorter than 0.5 ms, and requires a packet error rate of10⁻⁵ or less at the same time. Accordingly, for the service supportingthe URLLC, the 5G system should provide a transmit time interval (TTI)that is smaller than that of other services, and also requires designrequirements to assign wide resources in the frequency band in order tosecure reliability of communication links.

The three kinds of 5G services, that is, the eMBB, URLLC, and mMTC, maybe multiplexed and transmitted in one system. In this case, in order tosatisfy different requirements of the respective services, differenttransmission/reception techniques and transmission/reception parametersmay be used among the services.

Hereinafter, a frame structure of a 5G system will be described in moredetail with reference to the drawings.

FIG. 1 illustrates a diagram of the basic structure of a time-frequencydomain that is a radio resource region in which data or a controlchannel is transmitted in a 5G system.

With reference to FIG. 1, a horizontal axis represents a time domain,and a vertical axis represents a frequency domain. In the time andfrequency domains, the basic unit of resources is a resource element(RE) 101, which may be defined as one orthogonal frequency divisionmultiplexing (OFDM) symbol 102 on a time axis and as one subcarrier 103on a frequency axis. In the frequency domain, (e.g., 12) successive REsmay constitute one resource block (RB) 104.

FIG. 2 illustrates a diagram of a slot structure that is considered in a5G system.

FIG. 2 illustrates an example of structures of a frame 200, subframe201, and slot 202. One frame 200 may be defined as 10 ms. One subframe201 may be defined as 1 ms, and thus one frame 200 may be composed of 10subframes 201 in total. One slot 202 or 203 may be defined as 14 OFDMsymbols (i.e., the number of symbols N_(symb) ^(slot) for one slot=14).The subframe 201 may be composed of one or a plurality of slots 202 and203, and the number of slots 202 and 203 for one subframe 201 may differdepending on a configuration value μ 204 or 205 for subcarrier spacing.In an example of FIG. 2, cases where the configuration value μ for thesubcarrier spacing is μ=0 204 and μ=1 205 are illustrated. If μ=0 204,one subframe 201 may be composed of one slot 202, whereas if μ=1 205,one subframe 201 may be composed of two slots 203. That is, the numberof slots N_(slot) ^(subframe,μ) for one subframe may differ depending onthe configuration value μ for the subcarrier spacing, and thus thenumber of slots N_(slot) ^(frame,μ) for one frame may also differ. Thenumbers N_(slot) ^(subframe,μ) and N_(slot) ^(frame,μ) in accordancewith the configuration value μ for each subcarrier spacing may bedefined as in Table 1 below.

TABLE 1 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16 5 14 320 32

Next, bandwidth part (BWP) configuration in a 5G communication systemwill be described in detail with reference to the drawings. FIG. 3illustrates a diagram of an example of bandwidth part configuration in a5G communication system.

FIG. 3 shows an example in which a terminal (UE) bandwidth is configuredto include two bandwidth parts, that is, bandwidth part #1 301 andbandwidth part #2 302. A base station may configure one or a pluralityof bandwidth parts for the terminal, and may configure followinginformation with respect to the respective bandwidth parts.

TABLE 2 BWP ::=      SEQUENCE {   bwp-Id        BWP-Id,   (Bandwidthpart identifier)   locationAndBandwidth  INTEGER (1..65536),   (Locationof bandwidth part)   subcarrierSpacing    ENUMERATED {n0, n1, n2, n3,n4, n5},   (Subcarrier spacing)   cyclicPrefix        ENUMERATED {extended }   (Cyclic prefix) }

In addition to the configuration information as described above, variousparameters related to the bandwidth parts may be configured for theterminal. The above-described information may be transferred from thebase station to the terminal, for example, through higher layersignaling, for example, RRC signaling. One configured bandwidth part orat least one of a plurality of bandwidth parts may be activated. Whetherto activate the configured bandwidth part may be semi-staticallytransferred from the base station to the terminal through RRC signaling,or may be dynamically transferred through DCI. The terminal before anRRC connection may be configured with an initial bandwidth part (BWP)for an initial connection from the base station through a masterinformation block (MIB). More specifically, the terminal, at an initialconnection stage, may receive configuration information on a controlresource set (CORESET) capable of transmitting a PDCCH for receivingsystem information (which may correspond to remaining system information(RMSI) or system information block 1 (SIB1)) that is necessary for theinitial connection and search spaces through the MIB. The controlresource set and the search spaces configured through the MIB may berespectively considered as identity (ID) 0. The base station may notifythe terminal of configuration information, such as frequency assignmentinformation on a control resource set #0, time assignment information,and numerology, through the MIB. Further, the base station may notifythe base station of configuration information on a monitoring period andoccasion for the control resource set #0, that is, configurationinformation for a search space #0, through the MIB. The terminal mayconsider a frequency region configured as the control resource set #0acquired from the MIB as the initial bandwidth part for the initialconnection. In this case, an identity (ID) of the initial bandwidth partmay be considered as 0.

The configuration of the bandwidth parts supported in the 5G may be usedfor various purposes.

As an example, if the bandwidth supported by the terminal is less thanthe system bandwidth, this may be supported through the bandwidth partconfiguration. For example, by configuring a frequency location(configuration information 2) of a bandwidth part at Table 2 asdescribed above to the terminal, the terminal can transmit and receivedata at a specific frequency location in the system bandwidth.

As another example, the base station may configure a plurality ofbandwidth parts to the terminal for the purpose of supporting differentnumerologies. For example, in order for a certain terminal to supportdata transmission and reception using both a subcarrier spacing of 15kHz and a subcarrier spacing of 30 kHz, two bandwidth parts may beconfigured as subcarrier spacing of 15 kHz and 30 kHz, respectively. Thedifferent bandwidth parts may be frequency-division-multiplexed, and incase of transmitting and receiving data with specific subcarrierspacing, the bandwidth part that is configured with the correspondingsubcarrier spacing may be activated.

As another example, the base station may configure bandwidth partshaving bandwidths of different sizes to the terminal for the purpose ofreducing power consumption of the terminal. For example, if the terminalsupports a very high bandwidth, for example, a bandwidth of 100 MHz, andit transmits and receives data always with the corresponding bandwidth,this may cause quite high power consumption. In particular, from theviewpoint of the power consumption, it is very inefficient to performmonitoring of unnecessary downlink control channels with the highbandwidth of 100 MHz in a situation that no traffic exists. For thepurpose of reducing the power consumption of the terminal, the basestation may configure a bandwidth part having a relatively lowbandwidth, for example, a bandwidth part of 20 MHz, to the terminal. Inthe situation of no traffic, the terminal may perform a monitoringoperation in the bandwidth part of 20 MHz, and in case of dataoccurrence, the terminal may transmit and receive data with thebandwidth part of 100 MHz in accordance with instructions of the basestation.

In a method for configuring the bandwidth parts, terminals before beingRRC-connected may receive configuration information of the initialbandwidth part through the master information block (MIB) at the initialconnection stage. More specifically, the terminal may be configured witha control resource set (CORESET) for a downlink control channel capableof transmitting downlink control information (DCI) for scheduling asystem information block (SIB) from the MIB of a physical broadcastchannel (PBCH). The bandwidth of the control resource set configuredthrough the MIB may be considered as the initial bandwidth part, and theterminal may receive a PDSCH on which the SIB is transmitted through theconfigured initial bandwidth part. In addition to the purpose ofreceiving the SIM, the initial bandwidth part may be utilized for othersystem information (OSI), paging, and random access.

Next, a synchronization signal (SS)/PBCH block in 5G will be described.

The SS/PBCH block means a physical layer channel block composed of aprimary SS (PSS), a secondary SS (SSS), and a PBCH, and the detailsthereof are as follows.

-   -   PSS: This is a reference signal of downlink time/frequency        synchronization, and it provides partial information of a cell        ID.    -   SSS: This is a reference signal of downlink time/frequency        synchronization, and it provides remaining cell ID information        that is not provided by the PSS. In addition, the SSS may serve        as a reference signal for demodulating the PBCH.    -   PBCH: This provides essential system information necessary for        transmission/reception of a data channel and a control channel        of the terminal. The essential system information may include        search space related control information indicating radio        resource mapping information of the control channel and        scheduling control information on a separate data channel for        transmitting the system information.    -   SS/PBCH block: An SS/PBCH block is composed of a combination of        the PSS, SSS, and PBCH. One or a plurality of SS/PBCH blocks may        be transmitted within a time of 5 ms, and the respective SS/PBCH        blocks may be discriminated from each other by indexes.

At an initial connection stage, the terminal may detect the PSS and theSSS, and it may decode the PBCH. The terminal may acquire the MIB fromthe PBCH, and it may be configured with a control resource set #0 fromthe acquired MIB. The terminal may perform monitoring of the controlresource set #0 under the assumption that the selected SS/PBCH block anda DMRS transmitted from the control resource set #0 are quasi co located(QCL) with each other. The terminal may receive the system informationthrough the downlink control information transmitted from the controlresource set #0. The terminal may acquire configuration informationrelated to a random access channel (RACH) that is necessary for theinitial connection from the received system information. The terminalmay transmit a physical RACH (PRACH) to the base station inconsideration of the SS/PBCH index selected by the terminal itself, andthe base station having received the PRACH may acquire information onthe SS/PBCH block index selected by the terminal from the receivedPRACH. Through this, the base station can be aware of the fact thatwhich of the respective SS/PBCH blocks the terminal has selected andwhether the terminal has monitored the control resource set #0 relatedto the selected block.

Next, downlink control information (DCI) in a 5G system will bedescribed in detail.

In the 5G system, scheduling information on uplink data (or physicaluplink shared channel (PUSCH)) or downlink data (or physical downlinkshared channel (PDSCH)) is transferred from the base station to theterminal through the DCI. The terminal may monitor a fallback DCI formatand a non-fallback DCI format with respect to the PUSCH or PDSCH. Thefallback DCI format may include a fixed field predefined between thebase station and the terminal, and the non-fallback DCT format mayinclude a configurable field.

The DCI may be transmitted on a physical downlink control channel(PDCCH) through a channel coding and modulation process. A cyclicredundancy check (CRC) is attached to a DCI payload, and the CRC isscrambled by a radio network temporary identifier (RNTI) correspondingto the identity of the terminal. Different RNTIs are used in accordancewith the purpose of a DCI message, for example, in accordance with aUE-specific data transmission, a power control command, or a randomaccess response. That is, the RNTI is not transmitted explicitly, but isincluded in a CRC computation process to be transmitted. In case ofreceiving the DCI message being transmitted on the PDCCH, the terminalidentifies the CRC using the assigned RNTI, and if the result ofidentifying the CRC is correct, the terminal can be aware that thecorresponding message has transmitted to the terminal. Hereinafter, thePDCCH transmission may be interchangeably used with the DCI transmissionon the PDCCH.

For example, the DCI scheduling the PDSCH on the system information (SI)may be scrambled by an SI-RNTI. The DCI scheduling the PDSCH on a randomaccess response (RAR) message may be scrambled by a RA-RNTI. The DCIscheduling the PDSCH on a paging message may be scrambled by a P-RNTI.The DCI notifying a slot format indicator (SFI) may be scrambled by anSFI-RNTI. The DCI notifying a transmit power control (TPC) may bescrambled by a TPC-RNTI. The DCI scheduling the UE-specific PDSCH orPUSCH may be scrambled by a cell RNTI (C-RNTI).

DCI format 0_0 may be used as a fallback DCI scheduling the PUSCH, andin this case, the CRC may be scrambled by the C-RNTI. The DCI format 0_0in which the CRC is scrambled by the C-RNTI may include, for example,the following information.

TABLE 3 Identifier for DCI formats-[1] bit Frequency domain resourceassignment- [ [ log₂(N_(RB) ^(UL, BWP) (N_(RB) ^(UL, BWP) + 1)/2 ] ]bits Time domain resource assignment-4 bits Frequency hopping flag-1bit. Modulation and coding scheme-5 bits New data indicator-1 bitRedundancy version-2 bits HARQ process number-4 bits Transmit powercontrol (TPC) command for scheduled PUSCH-[2] bits Uplink(UL)/supplementary UL (SUL) indicator-0 or 1 bit

DCI format 0_1 may be used as a non-fallback DCI scheduling the PUSCH,and in this case, the CRC may be scrambled by the C-RNTI. The DCI format0_1 in which the CRC is scrambled by the C-RNTI may include, forexample, the following information.

TABLE 4   Carrier indicator-0 or 3 bits   UL/SUL indicator-0 or 1 bit  Identifier for DCI formats-[1] bits   Bandwidth part indicator-0, 1 or2 bits   Frequency domain resource assignment  For resource allocationtype 0, ┌N_(RB) ^(UL,BWP)/P┐ bits  For resource allocation type 1,┌log₂(N_(RB) ^(UL,BWP)(N_(RB) ^(UL,BWP) + 1)/2┐ bits   Time domainresource assignment-1, 2, 3, or 4 bits   VRB-to-PRB mapping ((virtualresource block)-to-(physical resource block) mapping)-0 or 1 bit, onlyfor resource allocation type 1.  0 bit if only resource allocation type0 is configured;  1 bit otherwise.   Frequency hopping flag-0 or 1 bit,only for resource allocation type 1.  0 bit if only resource allocationtype 0 is configured;  1 bit otherwise.   Modulation and coding scheme-5bits   New data indicator-1 bit   Redundancy version-2 bits   HARQprocess number-4 bits   1st downlink assignment index-1 or 2 bits  1 bitfor semi-static HARQ-ACK codebook(for semi-static HARQ-ACK codebook);  2bits for dynamic HARQ-ACK codebook with single HARQ-ACK codebook (incase that dynamic HARQ-ACK codebook is used together with singleHARQ-ACK codebook).   2nd downlink assignment index-0 or 2 bits   2 bitsfor dynamic HARQ-ACK codebook with twHARQ-ACK sub- codebooks (in casethat dynamic HARQ-ACK codebook is used together with two HARQ-ACKcodebooks);   0 bit otherwise.   TPC command for scheduled PUSCH-2 bits  ${SRS}\mspace{14mu}{resource}\mspace{14mu}{indicator}\text{-}\mspace{14mu}\left\lceil {\log_{2}\left( {\sum\limits_{k = 1}^{L_{\max}}\;\begin{pmatrix}N_{SRS} \\k\end{pmatrix}} \right)} \right\rceil\mspace{14mu}{or}\mspace{14mu}\left\lceil {\log_{2}\;\left( N_{SRS} \right)} \right\rceil\mspace{14mu}{bits}$  $\left\lceil {\log_{2}\left( {\sum\limits_{k = 1}^{L_{\max}}\;\begin{pmatrix}N_{SRS} \\k\end{pmatrix}} \right)} \right\rceil\mspace{14mu}{bits}\mspace{14mu}{for}\mspace{14mu}{non}\text{-}{codebook}\mspace{14mu}{based}\mspace{14mu}{PUSCH}\mspace{14mu}{transmission}$(in-case that PUSCH transmission is not based on codebook);  ┌log₂(N_(SRS))┐ bits for codebook based PUSCH transmission (in casethat PUSCH transmission is based on codebook).   Precoding informationand number of layers-up to 6 bits   Antenna ports-up to 5 bits   SRSrequest-2 bits   CSI request (channel state information request)-0, 1,2, 3, 4, 5, or 6 bits   CBG transmission information (code block grouptransmission information)- 0, 2, 4, 6, or 8 bits   PTRS-DMRS association((phase tracking reference signal)-(demodulation reference signal)association)-0 or 2 bits.   beta_offset indicator-0 or 2 bits   DMRSsequence initialization (demodulation reference signal sequenceinitialization)-0 or 1 bit

DCI format 1_0 may be used as a fallback DCI scheduling the PDSCH, andin this case, the CRC may be scrambled by the C-RNTI. The DCI format 1_0in which the CRC is scrambled by the C-RNTI may include, for example,the following information.

TABLE 5 Identifier for DCI formats-[1] bit Frequency domain resourceassignment- [ [ log₂(N_(RB) ^(DL, BWP) (N_(RB) ^(DL, BWP) + 1)/2) ] ]bits Time domain resource assignment-4 bits VRB-to-PRB mapping-1 bitModulation and coding scheme-5 bits New data indicator-1 bit Redundancyversion-2 bits HARQ process number-4 bits Downlink assignment index-2bits TPC command for scheduled PUCCH-[2] bits PUCCH resource indicator(physical uplink control channel (PUCCH) resource indicator)-3 bitsPDSCH-to-HARQ feedback timing indicator-[3] bits

DCI format 1_1 may be used as a non-fallback DCI scheduling the PDSCH,and in this case, the CRC may be scrambled by the C-RNTI. The DCI format1_1 in which the CRC is scrambled by the C-RNTI may include, forexample, the following information.

TABLE 6 Carrier indicator-0 or 3 bits Identifier for DCI formats-[1]bits Bandwidth part indicator-0, 1 or 2 bits Frequency domain resourceassignment For resource allocation type 0, [ N_(RB) ^(DL, BWP)/P ] bitsFor resource allocation type 1, [ log₂(N_(RB) ^(DL, BWP)(N_(RB)^(DL, BWP) + 1)/2 ] bits Time domain resource assignment-1, 2, 3, or 4bits VRB-to-PRB mapping-0 or 1 bit, only for resource allocation type 1.0 bit if only resource allocation type 0 is configured; 1 bit otherwise.PRB bundling size indicator (physical resource block bundling sizeindicator)- 0 or 1 bit Rate matching indicator-0, 1, or 2 bits ZP CSI-RStrigger (zero-power channel state information reference signaltrigger)-0, 1, or 2 bits For transport block 1: Modulation and codingscheme-5 bits New data indicator-1 bit Redundancy version-2 bits Fortransport block 2: Modulation and coding scheme-5 bits New dataindicator-1 bit Redundancy version-2 bits HARQ process number-4 bitsDownlink assignment index-0 or 2 or 4 bits TPC command for scheduledPUCCH-2 bits PUCCH resource indicator-3 bits PDSCH-to-HARQ_feedbacktiming indicator-3 bits Antenna ports-4, 5 or 6 bits Transmissionconfiguration indication (TCI)-0 or 3 bits SRS request-2 bits CBGtransmission information-0, 2, 4, 6, or 8 bits CBG flushing outinformation (code block group flushing out information)-0 or 1 bit DMRSsequence initialization-1 bit

Hereinafter, a downlink control channel in a 5G communication systemwill be described in more detail with reference to the drawing. FIG. 4illustrates a diagram of an example of a control resource set (CORESET)for transmitting a downlink control channel in a 5G wirelesscommunication system. FIG. 4 shows an example in which a bandwidth part410 of a terminal (UE) is configured on a frequency axis, and twocontrol resource sets (control resource set #1 401 and control resourceset #2 402) are configured in one slot 420 on a time axis. The controlresource sets 401 and 402 may be configured to a specific frequencyresource 403 in the whole UE bandwidth part 410 on the frequency axis.On the time axis, one or a plurality of OFDM symbols may be configured,and this may be defined as a control resource set duration 404. In theexample of FIG. 4, the control resource set #1 401 is configured with acontrol resource set duration of two symbols, and the control resourceset #2 is configured with a control resource set duration of one symbol.

The control resource set in the 5G as described above may be configuredfrom the base station to the terminal through higher layer signaling(e.g., system information, master information block (MIB), and radioresource control (RRC) signaling). Configuration of the control resourceset to the terminal means providing of information, such as a controlresource set identity, a frequency location of the control resource set,and a control resource set symbol duration. For example, the controlresource set may include the following information.

TABLE 7 ControlResourceSet ::=       SEQUENCE {   -- Corresponds to L1parameter ′CORESET-ID′  controlResourceSetId       ControlResourceSetId,   (Control resourceset Identity)   frequencyDomainResources      BIT STRING (SIZE (45)),  (Frequency axis resource assignment information)  duration             INTEGER (1..maxCoReSetDuration),   (Time axisresource assignment information)   cce-REG-MappingType          CHOICE {  (CCE-to-REG mapping type)     interleaved           SEQUENCE {     reg-BundleSize         ENUMERATED {n2, n3, n6},     (REG bundlesize)      precoderGranularity         ENUMERATED {sameAsREG-bundle,allContiguousRBs},      interleaverSize           ENUMERATED {n2, n3,n6}      (Interleaver size)      shiftIndex  INTEGER(0..maxNrofPhysicalResourceBlocks-1)   OPTIONAL    (Interleaver Shift)    },   nonInterleaved            NULL   },  tci-StatesPDCCH         SEQUENCE(SIZE  (1..maxNrofTCI- StatesPDCCH))OF TCI-StateId      OPTIONAL,   (QCL configuration information)  tci-PresentInDCI        ENUMERATED {enabled}               OPTIONAL, -- Need S }

At Table 7, tci-StatesPDCCH (simply called “TCI state”) configurationinformation may include information on one or a plurality ofsynchronization signal (SS)/physical broadcast channel (PBCH) blockindexes that are in quasi co located (QCL) relations with the DMRStransmitted from the corresponding control resource set or channel stateinformation reference signal (CSI-RS) indexes. FIG. 5 illustrates adiagram of an example of a base unit of time and frequency resourcesconfiguring a downlink control channel that can be used in 5G. Withreference to FIG. 5, the base unit of the time and frequency resourcesconfiguring the control channel is called a resource element group (REG)503, and the REG 503 may be defined as one OFDM symbol 501 on a timeaxis and one physical resource block 502 on a frequency axis, that is,12 subcarriers. A downlink control channel assignment unit may beconfigured through concatenation of the REG 503.

As illustrated in FIG. 5, if the base unit for assigning the downlinkcontrol channel in the 5G is a control channel element (CCE) 504, oneCCE 504 may be composed of a plurality of REGs 503. With reference tothe REG 503 illustrated in FIG. 5 as an example, the REG 503 may becomposed of 12 REs, and if one CCE 504 is composed of 6 REGs 503, it maymean that one CCE 504 is composed of 72 REs. If a downlink controlresource set is configured, the corresponding resource set may becomposed of a plurality of CCEs 504, and a specific downlink controlchannel may be mapped onto one or a plurality of CCEs 504 to betransmitted in accordance with an aggregation level (AL) in the controlresource set. The CCEs 504 in the control resource set may bediscriminated by numbers, and in this case, the numbers may be assignedin accordance with a logical mapping method.

The base unit of the downlink control channel illustrated in FIG. 5,that is, the REG 503, may include all of REs onto which the DCI ismapped and a resource set onto which a DMRS 505 that is a referencesignal for decoding the REs is mapped. As illustrated in FIG. 5, threeDMRSs 505 may be transmitted in one REG 503.

The number of CCEs necessary to transmit the PDCCH may be 1, 2, 4, 8, or16 in accordance with the aggregation level (AL), and the differentnumbers of CCEs may be used to implement a link adaptation of thedownlink control channel. For example, if the aggregation level is AL=L,one downlink control channel may be transmitted through L CCEs. It isnecessary for a terminal to detect a signal in a state where theterminal does not know information on the downlink control channel, anda search space indicating a set of CCEs is defined for blind decoding.The search space is a set of downlink control channel candidatescomposed of CCEs that the terminal should attempt to decode on a givenaggregation level, and the terminal has a plurality of search spacesbecause there are several aggregation levels on which 1, 2, 4, 8, or 16CCEs are bound into one bundle. The search space set may be defined as aset of search spaces at all configured aggregation levels.

The search space may be classified into a common search space and aUE-specific search space. Terminals in a specific group or all terminalsmay monitor the common search space of a PDCCH in order to receivedynamic scheduling of system information or cell-common controlinformation such as a paging message. For example, PDSCH schedulingassignment information for transmitting an SIB including operatorinformation of a cell may be received by monitoring the common searchspace of the PDCCH. In case of the common search space, terminals of aspecific group or all terminals should receive the PDCCH, and thus thecommon search space may be defined as a pre-engaged CCE set. It may bepossible to receive scheduling assignment information of a UE-specificPDSCH or PUSCH through monitoring of the UE-specific search space of thePDCCH. The UE-specific search space may be UE-specifically defined as afunction of UE identity and various system parameters.

In 5G, parameters for search spaces for the PDCCH may be configured fromthe base station to the terminal through higher layer signaling (e.g.,SIB, MIB, and RRC signaling). For example, the base station mayconfigure, to the terminal, the number of PDCCH candidates at eachaggregation level L, a monitoring period for search spaces, a monitoringoccasion of an intra-slot symbol unit for search spaces, a search spacetype (common search space or UE-specific search space), a combination ofa DCI format and an RNTI intended to be monitored in correspondingsearch spaces, and control resource set indexes intended to monitor thesearch spaces. For example, the search space may include the followinginformation.

TABLE 8 SearchSpace ::=         SEQUENCE {   -- Identity of the searchspace. SearchSpaceId = 0 identifies the SearchSpace configured via PBCH(MIB) or ServingCellConfigCommon.  searchSpaceId           SearchSpaceId,   (Search space identity)  controlResourceSetId        ControlResourceSetId,   (Control resourceset identity)   monitoringSlotPeriodicityAndOffset   CHOICE {  (Monitoring slot level period)     sl1                NULL,    sl2                INTEGER (0..1),     sl4                INTEGER(0..3),     sl5                INTEGER (0..4),    sl8                INTEGER (0..7),     sl10               INTEGER(0..9),     sl16               INTEGER (0..15),    sl20               INTEGER (0..19)   }               OPTIONAL,  monitoringSymbolsWithinSlot       BIT STRING (SIZE (14))                  OPTIONAL,   (Monitoring symbols within slot)  nrofCandidates          SEQUENCE {   (the number of PDCCH candidatesper aggregation level)     aggregationLevel1         ENUMERATED {n0, n1,n2, n3, n4, n5, n6, n8},     aggregationLevel2         ENUMERATED {n0,n1, n2, n3, n4, n5, n6, n8},     aggregationLevel4         ENUMERATED{n0, n1, n2, n3, n4, n5, n6, n8},    aggregationLevel8         ENUMERATED {n0, n1, n2, n3, n4, n5, n6,n8},     aggregationLevel16         ENUMERATED {n0, n1, n2, n3, n4, n5,n6, n8}   },   searchSpaceType            CHOICE {   (Search space type)   -- Configures this search space as common search space (CSS) and DCIformats to monitor.     common             SEQUENCE {  (Common searchspace)    }    ue-Specific           SEQUENCE {  (UE-specific searchspace)     -- Indicates whether the UE monitors in this USS for DCIformats 0-0 and 1-0 or for formats 0-1 and 1-1.     formats            ENUMERATED {formats0-0-And- 1-0,formats0-1-And-1-1},      ...        }

The base station may configure one or a plurality of search space setsto the terminal in accordance with the configuration information. As anexample, the base station may configure search space set 1 and searchspace set 2 to the terminal, and it may configure to monitor DCI formatA scrambled by X-RNTI in the common search space in the search space set1 and to monitor DCI format B scrambled by Y-RNTI in the UE-specificsearch space in the search space set 2. According to the configurationinformation, one or a plurality of search space sets may exist in thecommon search space or the UE-specific search space. For example, searchspace set #1 and search space set #2 may be configured to the commonsearch space, and search space set #3 and search space set #4 may beconfigured to the UE-specific search space.

In the common search space, the following combinations of DCI formatsand RNTIs may be monitored.

-   -   DCI format 0_0/1_0 with CRC scrambled by C-RNTI, CS-RNTI,        SP-CSI-RNTI, RA-RNTI, TC-RNTI, P-RNTI, SI-RNTI    -   DCI format 2_0 with CRC scrambled by SFI-RNTI    -   DCI format 2_1 with CRC scrambled by INT-RNTI    -   DCI format 2_2 with CRC scrambled by TPC-PUSCH-RNTI,        TPC-PUCCH-RNTI    -   DCI format 2_3 with CRC scrambled by TPC-SRS-RNTI

In the UE-specific search space, the following combinations of DCIformats and RNTIs may be monitored.

-   -   DCI format 0_0/1_0 with CRC scrambled by C-RNTI, CS-RNTI,        TC-RNTI    -   DCI format 1_0/1_1 with CRC scrambled by C-RNTI, CS-RNTI,        TC-RNTI

The above-specified RNTIs may follow the following definitions andpurposes.

C-RNTI (Cell RNTI): UE-specific PDSCH scheduling purposes

TC-RNTI (Temporary Cell RNTI): UE-specific PDSCH scheduling purposes

CS-RNTI (Configured Scheduling RNTI): semi-statically configuredUE-specific PDSCH scheduling purposes

RA-RNTI (Random Access RNTI): PDSCH scheduling purposes at a randomaccess stage

P-RNTI (Paging RNTI): PDSCH scheduling purposes for transmitting paging

SI-RNTI (System Information RNTI): PDSCH scheduling purposes fortransmitting system information

INT-RNTI (Interruption RNTI): Purposes for notifying of whether topuncture PDSCH

TPC-PUSCH-RNTI (Transmit Power Control for PUSCH RNTI): Power controlcommand indication purposes on PUSCH

TPC-PUCCH-RNTI (Transmit Power Control for PUCCH RNTI): Power controlcommand indication purposes on PUCCH

TPC-SRS-RNTI (Transmit Power Control for SRS RNTI): Power controlcommand indication purposes for SRS

The above-specified DCI formats may follow the definitions below.

TABLE 9 DCI Format Purposes 0_0 Scheduling of PUSCH in one cell 0_1Scheduling of PUSCH in one cell 1_0 Scheduling of PDSCH in one cell 1_1Scheduling of PDSCH in one cell 2_0 Notifying a group of UEs of the slotformat 2_1 Notifying a group of UEs of the PRB(s) and OFDM symbol(s)where UE may assume no transmission is intended for the UE 2_2Transmission of TPC commands for PUCCH and PUSCH 2_3 Transmission of agroup of TPC commands for SRS transmissions by one or more UEs

In 5G, a plurality of search space sets may be configured by differentparameters (e.g., parameters of Table 8), and thus a set of search spacesets being monitored by the terminal may differ at each time. Forexample, in case that search space set #1 is configured in an X-slotperiod, and search space set #2 is configured in a Y-slot period in astate where X and Y are different from each other, the terminal maymonitor all of search space set #1 and search space set #2 in a specificslot, and it may monitor one of search space set #1 and search space set#2 in a specific slot. If a plurality of search space sets areconfigured to the terminal, the following conditions may be consideredin a method for determining search space sets that the terminal shouldmonitor.

[Condition 1: Restriction on the Maximum Number of PDCCH Candidates]

The number of PDCCH candidates that can be monitored per slot does notexceed M^(μ). The M^(μ) may be defined as the maximum number of PDCCHcandidates per slot in a cell in which the subcarrier spacing isconfigured to 15·2^(μ) kHz, and it may be defined as in the table below.

TABLE 10 Maximum number of PDCCH candidates per slot and per μ servingcell (M^(μ)) 0 44 1 36 2 22 3 20

[Condition 2: Restriction on the Maximum Number of CCEs]

The number of CCEs constituting the whole search space (here, the wholesearch space means a set of the total CCEs corresponding to unionregions of a plurality of search space sets) per slot does not exceedC^(μ). The C^(μ) may be defined as the maximum number of CCEs per slotin a cell in which the subcarrier spacing is configured to 15·2^(μ) kHz,and it may be defined as in the table below.

TABLE 11 Maximum number of CCEs per slot and per serving cell μ (C^(μ))0 56 1 56 2 48 3 32

For convenience in technology, a situation where all of the conditions 1and 2 are satisfied at a specific time is defined as “condition A.”Accordingly, a case where the condition A is not satisfied may mean acase where at least one of the conditions 1 and 2 is not satisfied. Thecase where the above-described condition A is not satisfied may occur inaccordance with the configuration of the search space sets of the basestation. If the above-described condition A is not satisfied at thespecific time, the terminal may select and monitor only a part of thesearch space sets configured to satisfy the condition A at thecorresponding time, and the base station may transmit the PDCCH on theselected search space set.

Methods for selecting a partial search space among all the configuredsearch space sets may be as follows.

[Method 1]

If the condition A for the PDCCH is not satisfied at the specific time(slot), the terminal (or the base station) may preferentially select asearch space set of which the search space type is configured to thecommon search space rather than the search space set of which the searchspace type is configured to the UE-specific search space among thesearch space sets existing at the corresponding time.

If all the search space sets of which the search space type isconfigured to the common search space are selected (i.e., if thecondition A is satisfied even after all the search spaces of which thesearch space type is configured to the common search space areselected), the terminal (or the base station) may select the searchspace sets of which the search space type is configured to theUE-specific search space. In this case, if there are a plurality ofsearch space sets of which the search space type is configured to theUE-specific search space, the search space set having a low search spaceset index may have a higher priority. In consideration of the priority,the UE-specific search space sets may be selected within a range inwhich the condition A is satisfied.

Hereinafter, a method for determining a restriction on the maximumnumber of PDCCH candidates and a restriction on the maximum number ofCCEs, in an environment in which carrier aggregation (CA) in 5G isperformed, will be described in detail.

For convenience in explanation of the disclosure hereinafter,explanation will be made in the first consideration of the carrieraggregation, but it will be apparent that the term “carrier aggregation”may be replaced by various expressions, such as dual connectivity,multiple connectivity, or multiple connectivity support in accordancewith the environment.

If the terminal may perform the carrier aggregation with respect to fouror more cells (which may be called “component carriers (CCs)” in thesame manner), the terminal may report capability for the number N^(cap)of downlink cells capable of monitoring PDCCH candidates to the basestation. If the terminal is configured with total N^(μ) cells in whichthe subcarrier spacing is configured to μ from the base station, theterminal may consider the following PDCCH candidate number restrictionM^(total,μ) and CCE number restriction C^(total,μ) with respect to theconfigured N^(μ) cells.M ^(total,μ)=min{N ^(μ) ·M ^(μ) ,└N ^(cap) ·M ^(μ) ·N ^(μ) /N^(total)┘}  [Mathematical expression 1]C ^(total,μ)=min{N ^(μ) ·C ^(μ) ,└N ^(cap) ·C ^(μ) ·N ^(μ) /N^(total)┘}  [Mathematical expression 2]

In the mathematical expressions 1 and 2 as described above, N^(total) isN^(total)=N⁰+N¹+N²+N³. The maximum numbers M^(total,μ) and C^(total,μ)in the mathematical expressions 1 and 2 are named “first restriction.”That is, the first restriction may be the restriction on the maximumnumber of PDCCH candidates and the maximum number of CCEs that can beapplied with respect to one or a plurality of cells in which thesubcarrier spacing is configured to μ in case that the terminal havingreported a PDCCH additional monitoring UE capability in the CA situationis configured with the carrier aggregation composed of equal to or morethan the specific number of cells.

The terminal may be configured with search space sets from the basestation, and in this case, it may be expected that the number of searchspace sets does not exceed the first restriction. That is, it may beexpected that the terminal monitors the search spaces composed of themaximum number M^(total,μ) of PDCCH candidates and the maximum numberC^(total,μ) of CCEs. The base station may configure the search spacesets to the terminal so that the search space sets configured to thecells in which the subcarrier spacing is configured to μ do not exceedthe first restriction. That is, the base station may configure thesearch space sets to the terminal so that the total number of PDCCHcandidates constituting the search space sets configured to the cells inwhich the subcarrier spacing is configured to μ does not exceedM^(total,μ), and the total number of CCEs does not exceed C^(total,μ).

Based on M^(μ) in the table 10 and C^(μ) in the table 11 as describedabove, the terminal is not required to monitor the PDCCH candidates thenumber of which is larger than min(M^(μ), M^(total,μ)) or to monitor theCCEs the number of which is larger than min(C^(μ), C^(total,μ)) withrespect to activated bandwidth parts in which the subcarrier spacing isconfigured to μ in the individually scheduled cells, and the configurednumbers are named “second restriction”. That is, the second restrictionmay be the restriction on the maximum number of PDCCH candidates and themaximum number of CCEs that can be applied to a specific cell in whichthe subcarrier spacing is configured to μ regardless of the UEcapability report or the number of cells configuring the carrieraggregation.

In configuring a search space set for a specific cell (e.g., PCell) tothe terminal, the base station may notify the terminal of theconfiguration that does not satisfy the above-described condition A at aspecific time, that is, of the configuration including the PDCCHcandidates or CCEs the number of which is larger than M^(total,μ) of thetable 10 or C^(μ) of the table 11. If the search space of the specificcell exceeds the second restriction when the terminal monitors thesearch space at the specific time in accordance with the search spaceconfiguration of the base station, the terminal may selectively monitorthe specific search space set using the procedure of [method 1] asdescribed above.

The base station may configure the search space set with respect to asecondary cell so that the search space set does not exceed thecondition A at all times. The terminal may expect the search space setconfiguration that does not exceed the condition A at all times withrespect to the secondary cell.

FIG. 6 illustrates a diagram of an example in which restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs areapplied in a carrier aggregation environment.

In FIG. 6, total six cells CC#1 601, CC#2 602, CC#3 603, CC#4 604, CC#5605, and CC#6 606 are configured. The cells CC#1 601, CC#2 602, and CC#3603 are configured with a subcarrier spacing of μ=0 (corresponding to 15kHz), the cells CC#4 604 and CC#5 605 are configured with a subcarrierspacing of μ=1 (corresponding to 30 kHz), and the cell CC#6 606 isconfigured with a subcarrier spacing of μ=2 (corresponding to 60 kHz).Accordingly, in an example of FIG. 6, the numbers are configured toN⁰=3, N¹=2, N²=1, and N^(total)=6. The terminal may report, to the basestation, a capability value N^(cap) for the number of downlink cells formonitoring the PDCCH candidates. In the example, it is assumed thatN^(cap)=4.

With respect to the cells CC#1 601, CC#2 602, and CC#3 603 with thesubcarrier spacing of μ=0, a value 607 in accordance with the firstrestriction 620 on the number of PDCCH candidates may be calculated asfollows.M ^(total,0)=min{N ⁰ ·M ⁰ ,└N ^(cap) ·M ⁰ ·N ⁰ /N ^(total) ┘}=└N ^(cap)·M ⁰ ·N ⁰ /N ^(total)┘=88  [Mathematical expression 3]

With respect to the cells CC#4 604 and CC#5 605 with the subcarrierspacing of μ=1, a first restriction value 608 on the number of PDCCHcandidates may be calculated as follows.M ^(total,1)=min{N ¹ ·M ¹ ,└N ^(cap) ·M ¹ ·N ¹ /N ^(total) ┘}=└N ^(cap)·M ¹ ·N ¹ /N ^(total)┘=48  [Mathematical expression 4]

With respect to the cell CC#6 606 with the subcarrier spacing of p=2, afirst restriction value 609 on the number of PDCCH candidates may becalculated as follows.M ^(total,2)=min{N ² ·M ² ,└N ^(cap) ·M ² ·N ² /N ^(total) ┘}=└N ^(cap)·M ² ·N ² /N ^(total)┘=14  [Mathematical expression 5]

In consideration of the table 10, with respect to the cells CC#1 601,CC#2 602, and CC#3 603 with the subcarrier spacing of μ=0, a value inaccordance with the second restriction 630 on the number of PDCCHcandidates may be determined as M⁰=44 (610, 611, 612), and with respectto the cells CC#4 604 and CC#5 605 with the subcarrier spacing of μ=1, asecond restriction value on the number of PDCCH candidates may bedetermined as M¹=36 (613, 614). With respect to the cell CC#6 606 withthe subcarrier spacing of μ=2, a second restriction value on the numberof PDCCH candidates may be determined as M²=22 (615).

Although the restriction values for the number of PDCCH candidates havebeen described as an example, the restriction value C^(total,μ) on thenumber of CCEs can also be calculated in the same method.

If a cell which performs scheduling (i.e., a cell in which downlinkcontrol information for scheduling is transmitted or a cell in which theterminal performs monitoring of the PDCCH in the same manner) and a cellto which scheduling is applied (i.e., a cell in whichtransmission/reception of a data channel is performed in accordance withscheduling information of the received downlink control information or acell in which the terminal transmits/receives the data channel based onthe downlink control information in the same manner) have differentsubcarrier spacing in an environment in which the base station and theterminal operate to perform cross-scheduling based carrier aggregationin 5G, the maximum PDCCH candidate number restriction and the maximumCCE number restriction as defined above may be determined based on thesubcarrier spacing of the “first cell”.

More specifically, if the terminal may perform the carrier aggregationwith respect to four or more cells, the terminal may report thecapability for the number N^(cap) of downlink cells capable ofmonitoring the PDCCH candidates to the base station. The terminal may beconfigured with a plurality of cells for the purpose of the carrieraggregation. For example, the terminal may be configured with totalN^(μ) cells from the base station, and N^(total) may be defined asN^(total)=N⁰+N¹+N²+N³. Here, N^(μ) may means the number of cells inwhich the subcarrier spacing is configured to μ The respective cells maybe configured and operated through self-scheduling or cross-scheduling.The cells configured through cross-carrier scheduling may have differentsubcarrier spacing. That is, if the subcarrier spacing of the first cellis μ₁, and the subcarrier spacing of the second cell is μ₂, it may beconfigured that μ₁≠μ₂.

In this case, in a method for calculating the first restriction on thecells in which the subcarrier spacing is configured to μ (i.e., themaximum number of PDCCH candidates that can be applied with respect toone or a plurality of cells in which the subcarrier spacing isconfigured to μ), the subcarrier spacing μ₂ of the second cell to whichthe cross-scheduling is applied may be considered and calculated as thesubcarrier spacing μ₁ of the first cell performing the cross-scheduling.That is, M^(total,μ) may be calculated by the following mathematicalexpression.M ^(total,μ)=min{N ₀ ^(μ) ·M ^(μ) ,└N ^(cap) ·M ^(μ) ·N ₀ ^(μ) /N^(total)┘}  [Mathematical expression 6]

Here, it may be defined that N₀ ^(μ)=N₁ ^(μ)+N₂ ^(μ), and N₁ ^(μ) may bedefined as the number of cells in which the subcarrier spacing to whichthe self-scheduling is applied is μ, and N₂ ^(μ) may be defined as thetotal number of cells in which the subcarrier spacing of thecorresponding first cell is μ among the cells corresponding to thesecond cell to which the cross-scheduling is applied.

In the same manner, in a method for calculating the second restrictionon the cells in which the subcarrier spacing is configured to μ (i.e.,the maximum number of PDCCH candidates that can be applied to a specificcell in which the subcarrier spacing is configured to μ), the subcarrierspacing μ₂ of the second cell to which the cross-scheduling is appliedmay be considered and calculated as the subcarrier spacing μ₁ of thefirst cell performing the cross-scheduling. That is, the value M^(μ2) ofthe second cell may be considered as M^(μ1).

Because the terminal can perform the PDCCH monitoring for the secondcell in the search space configured to the first cell, it may bepreferable to calculate the restriction on the maximum number of PDCCHcandidates based on the subcarrier spacing of the first cell.

FIG. 7 illustrates a diagram of an example of a method for calculatingthe maximum number of PDCCH candidates according to a first embodimentof the disclosure.

FIG. 7 illustrates an example in which total six cells CC#1 701, CC#2702, CC#3 703, CC#4 704, CC#5 705, and CC#6 706 are configured. Thecells CC#1 701, CC#2 702, and CC#3 703 are configured with a subcarrierspacing of μ=0 (corresponding to 15 kHz), the cells CC#4 704 and CC#5705 are configured with a subcarrier spacing of μ=1 (corresponding to 30kHz), and the cell CC#6 706 is configured with a subcarrier spacing ofμ=2 (corresponding to 60 kHz). Accordingly, in an example of FIG. 7, thenumbers are configured to N⁰=3, N¹=2, N²=1, and N^(total)=6. Theterminal may report, to the base station, a capability value N^(cap) forthe number of downlink cells for monitoring the PDCCH candidates. In anexample of FIG. 7, it is assumed that N^(cap)=4.

In an example of FIG. 7, the cells CC#1 701, CC#3 703, CC#5 705, andCC#6 706 correspond to cells in which scheduling may be performed asself-scheduling, and the cells CC#2 702 and CC#4 704 correspond to cellsin which scheduling may be performed as cross-scheduling. In this case,the first cell performing cross-scheduling of CC#2 702 and CC#4 704 maybe CC#1 701. CC#1 701 that is the first cell and CC#2 702 that is thesecond cell may have the same subcarrier spacing (e.g., μ₁=μ₂=μ=0), andCC#1 701 that is the first cell and CC#4 704 that is the second cell mayhave different subcarrier spacing (e.g., μ₁=0, and μ₂=1).

In this case, in calculating M^(total,μ) according to the firstembodiment of the disclosure, M^(total,μ) may be calculated inconsideration of the subcarrier spacing of CC#2 702 and CC#4 702corresponding to the second cell as the subcarrier spacing of CC#1 701corresponding to the first cell. That is, M^(total,μ) may be calculatedin a state where the subcarrier spacing of CC#4 704 corresponding to thesecond cell having the subcarrier spacing that is different from thesubcarrier spacing of the first cell is considered as μ=0. That is, asillustrated in FIG. 7, in case of calculating M^(total,0), total fourcells CC#1 701, CC#2 702, CC#3 703, and CC#4 704 including CC#4 704 maybe considered (707), and in case of calculating M^(total,1), CC#4 704may be excluded, and one cell CC#5 705 may be included (708). In case ofcalculating M^(total,2), one cell CC#6 706 may be included (709).

Through computation in accordance with the first restriction 720 asdescribed above based on the mathematical expression 5, the valueM^(total,μ) may be calculated as in the following mathematicalexpression 7.M ^(total,0)=min{N ₀ ⁰ ·M ⁰ ,└N ^(cap) ·M ⁰ ·N ₀ ⁰ /N ^(total) ┘}=└N^(cap) ·M ⁰ ·N ₀ ⁰ /N ^(total)┘=└4·44·4/6┘=117,M ^(total,1)=min{N ₀ ¹ ·M ¹ ,└N ^(cap) ·M ¹ ·N ₀ ¹ /N ^(total) ┘}=└N^(cap) ·M ¹ ·N ₀ ¹ /N ^(total)┘=└4·36·1/6┘=24,M ^(total,2)=min{N ₀ ² ·M ² ,└N ^(cap) ·M ² ·N ₀ ² /N ^(total) ┘}=└N^(cap) ·M ² ·N ₀ ² /N ^(total)┘=└4·22·1/6┘=14  [Mathematical expression7]

In the same manner, in case of determining the value in accordance withthe second restriction 730 on CC#4 704, the value may not be determinedas M¹ in consideration of the subcarrier spacing μ=1 of CC#4 704 that isthe second cell, but the value may be determined as M⁰ in considerationof the subcarrier spacing μ=0 of CC#1 701 corresponding to the firstcell of CC#4 704 (710).

The terminal may be configured with a search space set for each cellfrom the base station, and in this case, it may be expected that thesearch space set does not exceed the first restriction calculated asabove. That is, the base station may configure search space sets to theterminal so that the total number of PDCCH candidates, which constitutethe search space sets configured to the cells corresponding to thesecond cell in which the subcarrier spacing of the first cell performingscheduling is configured to p, does not exceed M^(total,μ) whileperforming cross-scheduling with the cells in which the subcarrierspacing is configured to pt as self-scheduling is performed.

In configuring the search space set for the specific cell to theterminal, the base station may notify the terminal of the search spaceconfiguration that exceeds the second restriction calculated as above atthe specific time (corresponding to a case where the above-describedcondition A is not satisfied). That is, the second restriction on thecells corresponding to the second cell to which cross-scheduling isapplied may be calculated from the subcarrier spacing of the first cellperforming cross-scheduling of the corresponding cell. When the terminalmonitors the search space of the specific cell at the specific time inaccordance with the search space configuration of the base station, thesearch space set may exceed the second restriction. In this case, theterminal may selectively monitor the specific search space set in theprocedure of the above-described [method 1].

The base station may configure the search space set with respect to thesecondary cell so that the search space set does not exceed the secondrestriction at all times. The terminal may expect the search space setconfiguration that does not exceed the second restriction at all timeswith respect to the secondary cell.

FIG. 8 illustrates a diagram of radio protocol structures of a basestation and a terminal during performing of single cell, carrieraggregation (CA), and dual connectivity (DC) according to an embodimentof the disclosure.

With reference to FIG. 8, the radio protocol of the next-generationmobile communication system includes NR service data adaptation protocol(NR SDAP) 825 and 870, NR packet data convergence protocol (NR PDCP) 830and 865, NR radio link control (NR RLC) 835 and 860, and NR mediumaccess control (NR MAC) 840 and 855 in a terminal 804 and an NR basestation 802.

The primary functions of the NR SDAP 825 and 870 may include some of thefollowing functions.

-   -   Transfer of user plane data    -   Mapping between a QoS flow and a data bearer (DRB) for both a        downlink (DL) and an uplink (UL)    -   Marking QoS flow ID in both downlink (DL) and uplink (UL)        packets    -   Reflective QoS to data bearer (DRB) mapping for uplink (UL) SDAP        PDUs

With respect to the SDAP layer device, the terminal may be configuredwith an RRC message indicating whether to use a header of the SDAP layerdevice or whether to use the function of the SDAP layer device by PDCPlayer devices, bearers, or logical channels, and if the SDAP header isconfigured, this may be indicated by a NAS reflective QoS configurationone-bit indicator and an AS reflective QoS configuration one-bitindicator of the SDAP header so that the terminal can update orreconfigure UL and DL QoS flows and mapping information on the databearers. The SDAP header may include QoS flow ID information indicatingthe QoS. The QoS information may be used as a data processing priorityfor supporting smooth services, scheduling information, and so on.

The primary functions of the NR PDCP 830 and 865 may include some of thefollowing functions.

-   -   Header compression and decompression: ROHC only    -   Transfer of user data    -   In-sequence delivery of upper layer PDUs    -   Out-of-sequence delivery of upper layer PDUs    -   PDCP PDU reordering for reception    -   Duplicate detection of lower layer SDUs    -   Retransmission of PDCP SDUs    -   Ciphering and deciphering    -   Timer-based SDU discard in uplink

Among the above-described functions, the reordering of the NR PDCPdevice means reordering of PDCP PDUs received from a lower layer basedon PDCP sequence numbers (SN), and it may include transferring of datato a higher layer in the order of the reordering, direct transferringwithout considering the order, recording of the lost PDCP PDUs throughthe reordering, performing of a status report for the lost PDCP PDUs toa transmission side, or requesting for retransmission of the lost PDCPPDUs.

The primary functions of the NR RLC 835 and 860 may include some of thefollowing functions.

-   -   Transfer of upper layer PDUs    -   In-sequence delivery of upper layer PDUs    -   Out-of-sequence delivery of upper layer PDUs    -   Error correction through ARQ    -   Concatenation, segmentation, and reassembly of RLC SDUs    -   Re-segmentation of RLC data PDUs    -   Reordering of RLC data PDUs    -   Duplicate detection    -   Protocol error detection    -   RLC SDU discard    -   RLC re-establishment

Among the above-described functions, the in-sequence delivery of the NRRLC device means in-sequence transfer of the RLC SDUs received from alower layer to a higher layer, and this function may include reassemblyof the received RLC SDUs that are segmented from one original RLC SDU,reordering of the received RLC PDUs based on their RLC sequence numbers(SNs) or PDCP sequence numbers (SNs), recording of the lost RLC PDUsthrough the reordering, performing of a status report for the lost RLCPDUs to a transmission side, requesting for retransmission of the lostRLC PDUs, in-sequence transferring of only the RLC SDUs before beinglost to a higher layer in case that the lost RCL SDUs exist, in-sequencetransfer of all the RLC SDUs received before a specific timer starts toa higher layer in case that the timer has expired even if the lost RLCSDUs exist, or in-sequence transfer of all the RLC SDUs received up tothe present to a higher layer in case that a specific timer has expiredeven if the lost RLC SDUs exist. Further, the NR RLC device may processthe RLC PDUs in the order of their receptions (regardless of theirsequence number or the order of the sequence numbers, in the order oftheir arrival) and it may perform out-of-sequence delivery of the RLCPDUs to the PDCP device. If the received data is a segment, the NR RLCdevice may receive segments being stored in a buffer or to be receivedlater, reconfigure the received segments into one complete RLC PDU, andthen transfer the processed RLC PDU to the PDCP device. The NR RLC layermay not include a concatenation function, and the function may beperformed on an NR MAC layer or it may be replaced by a multiplexingfunction of the NR MAC layer.

The out-of-sequence delivery of the NR RLC device may mean the transferof the RLC SDUs received from a lower layer directly to a higher layerregardless of their order, and if one original RLC SDU is segmented intoseveral RLC SDUs to be received, the out-of-sequence delivery mayinclude reassembly and transfer of the received RLC SDUs, and recordingof the lost RLC PDUs through storing and reordering of the RLC SNs orPDCP SNs of the received RLC PDUs.

The NR MAC 840 and 855 may be connected to several NR RLC layer devicesconfigured in one terminal, and the primary functions of the NR MAC mayinclude some of the following functions.

-   -   Mapping between logical channels and transport channels    -   Multiplexing/demultiplexing of MAC SDUs    -   Scheduling information reporting    -   Error correction through HARQ    -   Priority handling between logical channels of one UE    -   Priority handling between UEs by means of dynamic scheduling    -   MBMS service identification    -   Transport format selection    -   Padding

An NR PHY layer 845 and 850 may perform channel coding and modulation ofhigher layer data, make and transmit OFDM symbols on a radio channel,and perform demodulation and channel decoding of the OFDM symbolsreceived on the radio channel to transfer the demodulated andchannel-decoded OFDM symbols to a higher layer.

The details of the radio protocol structure may be variously changed inaccordance with a carrier (or cell) operation method. As an example, incase that the base station transmits data to the terminal based on asingle carrier (or cell), the base station and the terminal use aprotocol structure having a single structure for each layer as indicatedby 800. In contrast, in case that the base station transmits data to theterminal based on the carrier aggregation (CA) using a multi-carrier ina single TRP, the base station 802 and the terminal 804 have a singlestructure until the RLC as indicated by 810, but they use the protocolstructure in which the PHY layer is multiplexed through a MAC layer.

As another example, in case that the base station transmits data to theterminal based on dual connectivity using multiple carriers at multipleTRPs, two base stations 806 and 808 and the terminal have a singlestructure until the RLC as indicated by 820, but they use the protocolstructure in which the PHY layer is multiplexed through the MAC layer.

In LTE and NR, the terminal has a procedure of reporting capabilitysupported by the terminal to the corresponding base station in a statewhere the terminal is connected to a serving base station. In thefollowing description, this is called UE capability (report). The basestation may transfer a UE capability enquiry message for requesting thecapability report to the terminal that is in a connected state with thebase station. The base station may request to include the UE capabilityfor each RAT type in the UE capability message. The request for each RATtype may include a request for UE capability information for a frequencyband. Further, in case of the UE capability enquiry message, one RRCmessage container may request the UE capability for a plurality of RATtypes, or the base station may transfer the UE capability enquirymessage including the request for each RAT type multiple times. That is,the UE capability enquiry may repeat multiple times, and the terminalmay configure and report the corresponding UE capability informationmessage multiple times. In the next-generation mobile communicationsystem, it is possible to request the UE capability for multi-radio dualconnectivity (MR-DC) including NR, LTE, and EN-DC. For reference, it isgeneral to initially send the UE capability enquiry message after theterminal is connected, but the base station may request the messageunder any condition when needed.

At the above-described stage, the terminal having received the UEcapability report request from the base station configures the UEcapability in accordance with the RAT type requested from the basestation and band information. Hereinafter, a method in which theterminal configures the UE capability in the NR system will bedescribed.

-   -   1. If the terminal is provided with a list of LTE and/or NR        bands from the base station through the UE capability request,        the terminal configures a band combination (BC) for cases of        EN-DC and NR stand-alone (SA). That is, the terminal configures        a candidate list of the BC for the EN-DC and the NR SA based on        the bands requested from the base station through FreqBandList.        Further, the band priority follows the order described in the        FreqBandList.    -   2. If the base station requests the UE capability report by        setting an “eutra-nr-only” flag or “eutra” flag, the terminal        completely removes those related to the NR SA and BC from the        candidate list of the BC configured as above. Such an operation        may be performed only in case that the LTE base station (eNB)        requests the “eutra” capability.    -   3. Thereafter, the terminal removes fallback BCs from the        candidate list of the BC configured at the above-described        stage. Here, the fallback BC corresponds to a case where a band        corresponding to at least one SCell is removed from a certain        super set BC, and the fallback BC can be omitted because the        super set BC can already cover the fallback BC. This stage is        applied even to the MR-DC, and thus this stage is applied even        to an LTE band. After this stage, the remaining BCs constitute a        final “candidate BC list”.    -   4. The terminal selects the BCs to be reported through selection        of the BCs to match the requested RAT type in the final        candidate BC list. At this stage, the terminal configures        supportedBandCombinationList in the determined order. That is,        the terminal configures the BC and UE capability to be reported        to match the order of a preconfigured rat-Type. The order may be        equal to nr→eutra-nr→eutra. Further, the terminal configures        featureSetCombination for the configured        supportedBandCombinationList, and it configures a list of        “candidate feature set combination” based on the candidate BC        list from which the list of fallback BCs (including capability        at the same or lower stage) is removed. The “candidate feature        set combination” includes all feature set combinations of the NR        and EUTRA-NR BC, and it can be obtained from the feature set        combinations of containers of UE-NR-Capabilities and        UE-MRDC-Capabilities.    -   5. Further, If the requested rat Type is eutra-nr, and it exerts        an influence on LTE and NR feature set configurations, the        featureSetCombinations may be included in two containers in all.        However, the NR feature set includes only UE-NR-Capabilities.

After the UE capability is configured, the terminal transfers a UEcapability information message including the UE capability to the basestation. Thereafter, the base station performs scheduling andtransmission/reception management suitable to the corresponding terminalbased on the UE capability received from the terminal.

In contrast with the existing system, the 5G wireless communicationsystem may support all of services requiring a high transmission speed,services having a very short transmission delay, and services requiringa high connection density. In a wireless communication network includinga plurality of cells, transmission and reception points (TRPs), orbeams, coordinated transmission between respective cells, TRPs, or/andbeams is one of core technologies capable of satisfying the variousservice requirements by increasing the strength of a signal received bythe terminal or efficiently performing an interference control betweenthe cells, TRPs, or/and beams.

Joint transmission (JT) is a representative transmission technology forthe coordinated transmission, and through the technology, the strengthof the signal received by the terminal may be increased by supportingone terminal through different cells, TRPs, or/and beams. Meanwhile,because the characteristics of channels between the cells, TRPs, or/andbeams and the terminal may greatly differ from each other, it isnecessary to apply different precoding, MCS, and resource assignment tolinks between the cells, TRPs, or/and beams and the terminal. Inparticular, in case of non-coherent joint transmission (NC-JT)supporting non-coherent precoding between the cells, TRPs, or/and beams,it is important to configure individual DL transmission information forthe cells, TRPs, or/and beams. Meanwhile, configuration of theindividual DL transmission information by cells, TRPs, or/and beams maybe an important factor to increase a payload necessary for DL DCItransmission, and this may exert a bad influence on the receptionperformance of a physical downlink control channel (PDCCH) fortransmitting the DCI. Accordingly, in order to support the JT, it isnecessary to carefully design a tradeoff between an amount of DCIinformation and the PDCCH reception performance.

FIG. 9A illustrates a diagram of a joint transmission (JT) techniqueaccording to an embodiment of the disclosure. In FIG. 9A, a (900)illustrates coherent joint transmission (C-JT) supporting coherentprecoding between respective cells, TRPs, or/and beams. In the C-JT, TRPA 905 and TRP B 910 transmit the same data (PDSCH), and a plurality ofTRPs perform joint precoding. This means that the TRP A 905 and the TRPB 910 perform transmission in accordance with the same DMRS ports (e.g.,DMRS ports A and B for the two TRPs) for the above-described PDSCHreception. In this case, the terminal 915 may receive one piece of DCIinformation for receiving one PDSCH demodulated by the DMRS ports A andB.

Meanwhile, b (920) illustrates non-coherent joint transmission (NC-JT)supporting non-coherent precoding between respective cells, TRPs, or/andbeams. In the NC-JT, different PDSCHs are transmitted through therespective cells, TRPs, or/and beams, and an individual precoding may beapplied to the respective PDSCHs. This means that TRP A 925 and TRP B930 perform transmission in accordance with different DMRS ports (e.g.,DMRS port A for TRP A and DMRS port B for TRP B) for reception of thedifferent PDSCHs. In this case, the terminal 935 may receive two kindsof DCI information for receiving PDSCH A that is demodulated by the DMRSport A and PDSCH B demodulated by the DMRS port B.

FIG. 9B illustrates a diagram of examples of radio resource assignmentper TRP in accordance with situations.

For example, in case of the NC-JT, it is possible to consider variousradio resource assignments in case that a plurality of TRPs use the samefrequency and time resources (940), in case that the frequency and timeresources used by a plurality of TRPs do not overlap each other at all(945), and in case that parts of the frequency and time resources usedby a plurality of TRPs overlap each other (950). In particular, in caseof 950, it can be known that a DCI payload necessary for resourceassignment information is linearly increased in relation to the numberof TRPs. The increase of the DL DCI payload as described above may exerta bad influence on the reception performance of a PDCCH for transmittingthe DCI or it may greatly increase DCI blind decoding complexity of theterminal as described above. In order to assign a plurality of PDSCHs toone terminal at the same time to support the NC-JT, the DCI havingvarious types, structures, and relations may be considered.

FIG. 10 illustrates a diagram of two examples of DCI designs forsupporting NC-JT according to an embodiment of the disclosure.

In FIG. 10, case #1 1000 is an example in which pieces of controlinformation 1010, 1012, and 1014 on PDSCHs transmitted from additionalTRPs (TRP #1 to TRP #N−1) are transmitted in the same DCI format as theformat of the control information on the PDSCHs transmitted from aserving TRP in a situation that the different (N−1) PDSCHs aretransmitted from the additional (N−1) (TRPs TRP#1 to TRP#(N−1) inaddition to the serving TRP TRP#0 used during a single PDSCHtransmission. That is, the terminal acquires the control information onthe PDSCHs transmitted from the different TRPs TRP#0 to TRP#(N−1)through pieces of DCI DCI#0 to DCI#(N−1), 1020, 1022, and 1024 havingthe same DCI format and the same payload. The case #1 has the advantagethat the degree of freedom of PDSCH control (assignment) is completelysecured, but it has the disadvantage that a coverage difference for eachDCI occurs to deteriorate the reception performance in case that the DCIis transmitted from different TRPs.

Meanwhile, case #2 1030 is an example in which pieces of controlinformation 1040, 1042, and 1044 on PDSCHs transmitted from additionalTRPs are transmitted from the same DCI as the control information on thePDSCHs transmitted from a serving TRP in a situation that the different(N−1) PDSCHs are transmitted from the additional (N−1) TRPs TRP#1 toTRP#(N−1) in addition to the serving TRP TRP#0 used during the singlePDSCH transmission. That is, the terminal acquires the controlinformation on the PDSCHs transmitted from the different TRPs TRP#0 toTRP#(N−1) through single DCI 1050. The case #2 has the advantage thatthe DCI blind decoding complexity of the terminal is not increased, butit has the disadvantage that the degree of freedom of PDSCH control(assignment) is low caused by restriction on the number of coordinatedTRPs in accordance with restriction on the DCI payload.

In the following explanation and embodiments, the case #1 in which morethan one DCI (PDCCH) is used to support the NC-JT is discriminated asthe multiple PDCCH based NC-JT, and the case #2 in which a single DCI(PDCCH) is used to support the NC-JT is discriminated as the singlePDCCH based NC-JT.

In embodiments of the disclosure, it is possible to replace the“coordinated TRP” by various terms, such as “coordinated panel” or“coordinated beam” during its actual application.

In embodiments of the disclosure, “the case where the NC-JT is applied”may be variously interpreted to match the situation, such as “the casewhere the terminal simultaneously receives at least one PDSCH from oneBWP”, “the case where the terminal simultaneously receives the PDSCHbased on at least two TCI indications from one BWP”, and “the case wherethe PDSCH received by the terminal is associated with at least one DMRSport group”, but one expression is used for convenience in explanation.

In the disclosure, the radio protocol structure for the NC-JT may bevariously used in accordance with TRP unfolding scenarios. As anexample, in case that a backhaul delay between coordinated TRPs does notexist or low backhaul delay exists, it is possible to use a structurebased on MAC layer multiplexing in a similar manner to 810 of FIG. 8(CA-like method). In contrast, in case that the backhaul delay betweenthe coordinated TRPs is high enough so that the backhaul delay is unableto be disregarded (e.g., if time equal to or more than 2 ms is requiredfor CSI exchange between the coordinated TRPs or scheduling informationexchange), it is possible to secure the characteristics robust to thedelay using an independent structure for each TRP from an RLC layer in asimilar manner to 820 of FIG. 8 (DC-like method).

In LTE and NR systems, the terminal may adjust PDCCH detection attemptcomplexity of the terminal by controlling restrictions on the maximumnumber of PDCCH candidates and the maximum number of control channelelements (CCEs) for control channel reception in one slot in accordancewith a specific condition, for example, in accordance with the number ofdownlink serving cells (which may be equally called “component carrier(CC)”) configured for the carrier aggregation.

Meanwhile, the terminal can be assigned with one or more PDSCHs at onetime for the purpose of performing coordinated communicationtransmission such as NC-JT, and in this case, respective PDSCHs may beassigned by different PDCCHs. Accordingly, if the coordinatedcommunication transmission is performed when a large number of servingcells exist in a state where the terminal control channel detectioncomplexity in the related art is maintained as it is, the number ofcontrol channels that should be actually transmitted in possible controlchannel resource sets is abruptly increased, and thus the degree offreedom of control channel transmission of the base station is greatlyreduced, and the control channel interference control performance maydeteriorate.

Various embodiments of the disclosure propose a method for determiningrestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs defined as above in an environment in which the carrieraggregation in 5G and the NC-JT operate at the same time.

Hereinafter, for simplicity in explanation in describing the disclosure,the restriction value M^(total,μ) on the number of PDCCH candidates willbe described as an example. This may be applied in the same manner incalculating the restriction value C^(total,μ) on the number of CCEs.

Hereinafter, for simplicity in explanation in describing the disclosure,a cell in which scheduling is performed is called a first cell, and acell to which scheduling information of the first cell is applied iscalled a second cell.

First Embodiment: Method for Managing Restrictions on the Maximum Numberof PDCCH Candidates and the Maximum Number of CCEs in Consideration ofan NC-JT

In the first embodiment, methods for managing restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs inconsideration of an NC-JT are provided.

For the NC-JT, it is possible for the base station to assign a pluralityof PDSCHs to the terminal in the same cell and bandwidth part at thesame time through a plurality of PDCCHs. If the base station determinesthe restrictions on the maximum number of PDCCH candidates and themaximum number of CCEs using only [condition A], [first restriction],and [second restriction] as described above in a situation where thebase station operates the NC-JT and the carrier aggregation at the sametime, the plurality of PDCCHs for the NC-JT should be transmitted withinthe restrictions on the maximum number of PDCCH candidates and themaximum number of CCEs, such as the plurality of PDCCHs for the carrieraggregation, and thus the degree of freedom of PDCCH transmission forthe existing carrier aggregation is unable to be maintained.

To solve this, it is possible to introduce “UE capability report foradditional PDCCH candidate monitoring” in addition to the UE capabilityreport for the number N^(cap) of downlink cells capable of monitoringthe PDCCH candidates, and thus to extend the restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs. The UEcapability report for the additional PDCCH candidate monitoring may benotification of whether carrier aggregation and separate additionalPDCCH candidate monitoring are possible or the degree of the additionalPDCCH candidate monitoring through additional signaling, for example,through pdcch-BlindDetectionNCJTϵ{1 or 2}, in addition topdcch-BlindDetectionCA that is the UE capability report for the PDCCHmonitoring for the carrier aggregation. This means that it is possibleto extend the restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs, if needed, even in case that the numberN^(cap) of downlink cells is not sufficiently large (e.g., is not largerthan 4).

Specifically, the base station can extend the restrictions on themaximum number of PDCCH candidates and the maximum number of CCEsthrough the following methods only with respect to the terminal havingperformed the UE capability report for the additional PDCCH candidatemonitoring among the terminals supporting the NC-JT.

[Method A]

According to [Method A], if corresponding signaling exists (e.g., ifpdcch-BlindDetectionNCJT is reported to the base station), therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs in the related art are increased in a specific ratio(e.g., twice) through the UE capability report for the additional PDCCHcandidate monitoring. The specific ratio may be one of a predeterminedvalue in accordance with the kind of the UE capability report for theadditional PDCCH candidate monitoring and a value indicated throughhigher layer signaling.

It is possible to engage for the UE capability report for the additionalPDCCH candidate monitoring so that a single value is applied to all thecells, or separate values are applied by frequency bands (e.g.,frequency range 1 equal to or lower than 6 GHz versus frequency range 2higher than 6 GHz), or separate values are applied by cellgroups/cells/bandwidth parts. Table 12 below presents an example of achange of restrictions on the maximum number of PDCCH candidates and themaximum number of CCEs by [Method A].

TABLE 12 If the terminal is configured with four or less downlink cellswith respect to possible subcarrier spacing μ = 0, 1, 2, 3 (Σ_(μ=0) ^(∂)N^(μ) ≤ 4), restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs follow M^(μ) of the table 10 and C^(μ) of thetable 11. If the terminal is configured with more than four downlinkcells with respect to possible subcarrier spacing μ = 0, 1, 2, 3(Σ_(μ=0) ^(∂) N^(μ) > 4), and reports the UE capability reportpdcch-BlindDetectionCA for PDCCH monitoring for carrier aggregation tothe base station, restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs follow the mathematical expression 1 andthe mathematical expression 2. If the terminal is configured with fouror less downlink cells with respect to possible subcarrier spacing μ =0, 1, 2, 3 (Σ_(μ=0) ^(∂) N^(μ) ≤ 4), and reports the UE capabilityreport pdcch-BlindDetectionNCJT for additional PDCCH candidatemonitoring to the base station, restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs follow X times (e.g., X= 2) M^(μ) of the table 10 and C^(μ) of the table 11. If the terminal isconfigured with more than four downlink cells with respect to possiblesubcarrier spacing μ = 0, 1, 2, 3 (Σ_(μ=0) ^(∂) N^(μ) > 4), and reportsthe UE capability report pdcch-BlindDetectionCA for PDCCH monitoring forcarrier aggregation to the base station, and reports the UE capabilityreport pdcch-BlindDetectionNCJT for additional PDCCH candidatemonitoring to the base station, restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs follow X times (e.g., X= 2) the mathematical expression 1 and the mathematical expression 2.

Table 13 below presents an example of a change of restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs by[Method A].

TABLE 13 If the terminal is configured with four or less downlink cellswith respect to possible subcarrier spacing μ = 0, 1, 2, 3 (Σ_(μ=0) ^(∂)N^(μ) ≤ 4), restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs follow M^(μ) of the table 10 and C^(μ) of thetable 11. If the terminal is configured with more than four downlinkcells with respect to possible subcarrier spacing μ = 0, 1, 2, 3(Σ_(μ=0) ^(∂) N^(μ) > 4), and reports the UE capability reportpdcch-BlindDetectionCA for PDCCH monitoring for carrier aggregation tothe base station, restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs follow the mathematical expression 1 andthe mathematical expression 2. If the terminal is configured with morethan four downlink cells with respect to possible subcarrier spacing μ =0, 1, 2, 3 (Σ_(μ=0) ^(∂) N^(μ) > 4), and reports the UE capabilityreport pdcch-BlindDetectionCA for PDCCH monitoring for carrieraggregation to the base station, and reports the UE capability reportpdcch-BlindDetectionNCJT for additional PDCCH candidate monitoring tothe base station, restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs follow mathematical expressions 8 and 9below. In the mathematical expression 8 and the mathematical expression9, X may be a value following a specific constant or a UE report, forexample, X may be X = 2. The mathematical expressions 8 and 9 may bebased on the mathematical expressions 1 and 2. [Mathematical expression8] M^(total, μ) = min{N^(μ) · M^(μ), [X · N^(cap) · M^(μ) ·N^(μ)/N^(total)]) [Mathematical expression 9] C^(total, μ) = min{N^(μ) ·C^(μ), [X · N^(cap) · C^(μ) · N^(μ)/N^(total)])

In addition to the tables 12 and 13, various modifications are possible,but are not enumerated herein in order to avoid obscuring of the gist ofthe explanation.

[Method B]

According to [Method B], if corresponding signaling exists (e.g., ifpdcch-BlindDetectionNCJT is reported to the base station), the conditionto control the restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs in the related art is extended throughthe UE capability report for the additional PDCCH candidate monitoring.It is possible to engage for the UE capability report for the additionalPDCCH candidate monitoring so that a single value is applied to all thecells, or separate values are applied by frequency bands (e.g.,frequency range 1 equal to or lower than 6 GHz versus frequency range 2higher than 6 GHz), or separate values are applied by cellgroups/cells/bandwidth parts.

As an example, if at least one condition is satisfied betweencondition 1) on which the terminal is configured with more than fourdownlink cells with respect to possible subcarrier spacing μ=0, 1, 2, 3,and the terminal reports the UE capability report pdcch-BlindDetectionCAfor PDCCH monitoring for carrier aggregation to the base station andcondition 2) on which the terminal reports the UE capability reportpdcch-BlindDetectionNCJT for additional PDCCH candidate monitoring tothe base station, it is possible to engage for the extension of therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs. Table 14 below presents an example of a change of therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs by [Method B].

TABLE 14 If the terminal is configured with four or less downlink cellswith respect to possible subcarrier spacing μ = 0, 1, 2, 3 (Σ_(μ=0) ^(∂)N^(μ) ≤ 4), restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs follow M^(μ) of the table 10 and C^(μ) of thetable 11. If the terminal is configured with more than four downlinkcells with respect to possible subcarrier spacing μ = 0, 1, 2, 3(Σ_(μ=0) ^(∂) N^(μ) > 4), and the terminal reports the UE capabilityreport pdcch-BlindDetectionCA for PDCCH monitoring for carrieraggregation to the base station, or reports the UE capability reportpdcch- BlindDetectionNCJT for additional PDCCH candidate monitoring tothe base station, restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs follow the mathematical expression 1 andthe mathematical expression 2.

In addition to the table 14, various modifications are possible, but arenot enumerated herein in order to avoid obscuring of the gist of theexplanation.

[Method C]

According to [Method C], if corresponding signaling exists (e.g., ifpdcch-BlindDetectionNCJT is reported to the base station), thedefinition of the number of downlink cells configured to the terminal inthe related art is changed through the UE capability report for theadditional PDCCH candidate monitoring. It is possible to engage for theUE capability report for the additional PDCCH candidate monitoring sothat a single value is applied to all the cells, or separate values areapplied by frequency bands (e.g., frequency range 1 equal to or lowerthan 6 GHz versus frequency range 2 higher than 6 GHz), or separatevalues are applied by cell groups/cells/bandwidth parts. As an example,if the UE capability report for the additional PDCCH candidatemonitoring is applied to all the cells, the terminal multiplies theconfigured number of downlink cells by the number of PDSCHs for theNC-JT (or the number of codewords or a value that is signaled orreported by the terminal), and if the value is larger than a specificvalue (e.g., 4), it is possible to engage for the extension of therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs. Table 15 below presents an example of a change of therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs by [Method C].

TABLE 15 If the terminal is configured with four or less downlink cellswith respect to possible subcarrier spacing μ = 0, 1, 2, 3 (Σ_(μ=0) ^(∂)N^(μ) ≤ 4), restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs follow M^(μ) of the table 10 and C^(μ) of thetable 11. If a condition Σ_(μ=0) ^(∂) X · N^(μ) ≤ 4 (e.g., X = 2), issatisfied by the number of downlink cells with which the terminal isconfigured with respect to possible subcarrier spacing μ = 0, 1, 2, 3,and the UE capability report pdcch-BlindDetectionNCJT for the additionalPDCCH candidate monitoring, restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs follow M^(μ) of the table 10and C^(μ) of the table 11. If the terminal is configured with more thanfour downlink cells with respect to possible subcarrier spacing μ = 0,1, 2, 3 (Σ_(μ=0) ^(∂) N^(μ) > 4), and the terminal reports the UEcapability report pdcch-BlindDetectionCA for PDCCH monitoring forcarrier aggregation to the base station, or reports the UE capabilityreport pdcch- BlindDetectionNCJT for additional PDCCH candidatemonitoring to the base station, restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs follow the mathematicalexpression 1 and the mathematical expression 2. If a condition Σ_(μ=0)^(∂) X · N^(μ) ≤ 4 (e.g., X = 2) is satisfied by the number of downlinkcells with which the terminal is configured with respect to possiblesubcarrier spacing μ = 0, 1, 2, 3 and the UE capability reportpdcch-BlindDetectionNCJT for the additional PDCCH candidate monitoring,restrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs follow the mathematical expression 1 and the mathematicalexpression 2.

In addition to the table 15, various modifications are possible, but arenot enumerated herein in order to avoid obscuring of the gist of theexplanation. It is possible to differently apply the restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs by[Method A] to [Method C] by frequency bands (e.g., frequency range 1equal to or lower than 6 GHz versus frequency range 2 higher than 6GHz).

In the present embodiment, [Method A] to [Method C] are not exclusive toeach other, but can be combined and applied together. For example,[Method C] may be applied in consideration of the mathematicalexpressions 3 and 4 in [Method A].

Hereinafter, for convenience in explanation, the restriction on themaximum number of PDCCH candidates and the maximum number of CCEs by[Method A] to [Method C] may be called a third restriction.

FIG. 11 illustrates a diagram of an operation of a terminal to determinerestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs according to an embodiment of the disclosure. Atoperation 1100, with respect to a base station, the terminal performs aUE capability report (e.g. pdcch-BlindDetectionCA) for PDCCH monitoringfor carrier aggregation and a UE capability report (e.g.pdcch-BlindDetectionNCJT) notifying whether additional PDCCH candidatemonitoring is possible and the degree of the additional PDCCH candidatemonitoring. At operation 1105, the base station performs higher layerconfigurations for downlink cells for carrier aggregation, whether anNC-JT transmission is possible, or whether multi-PDCCH based NC-JTtransmission is possible based on the UE capability reports. Thereafter,the base station and the terminal determine whether additional PDCCHblind decoding for CA is possible by the UE capability report andsubsequent higher layer configuration values (1110). If the additionalPDCCH blind decoding is not possible, the terminal performs PDCCH blinddecoding in accordance with the [condition A] (1120).

In contrast, if the additional PDCCH blind decoding is possible, theterminal additionally determines whether additional PDCCH blind decodingfor an NC-JT is possible (1115), and if the additional PDCCH blinddecoding for the NC-JT is not possible, the terminal determines whetherthe number of downlink cells configured for the carrier aggregation islarger than 4 (1130). If the number of downlink cells is equal to orsmaller than 4 as the result of the determination, the terminal mayperform PDCCH decoding without changing restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs (1120),whereas if the number of downlink cells is larger than 4, the terminalmay perform the PDCCH decoding by increasing the restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs, thatis, in accordance with a first restriction and a second restriction(1140).

If the additional PDCCH blind decoding for the NC-JT is possible as theresult of the determination at operation 1115, the terminal, atoperation 1125, may additionally determine whether the third restrictionis applicable in accordance with the above-described method (e.g.,depending on whether the maximum number of PDSCHs configured for the CAand NC-JT is equal to or larger than a specific value). In accordancewith the result of the determination, the terminal may perform the PDCCHdecoding without changing the restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs (1120), or the terminalmay perform the PDCCH decoding in accordance with the third restrictionand the second restriction by additionally increasing the restrictionson the maximum number of PDCCH candidates and the maximum number of CCEs(1135).

Further, the contents of FIG. 11 are applied to the base station, andthe base station may determine the restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs of the terminal inaccordance with the contents of FIG. 11.

Second Embodiment: Method for Processing PCell PDCCH Overbooking inConsideration of the NC-JT

In the second embodiment, in case of applying the NC-JT, the PDCCHresource is overbooked, that is, the restrictions on the maximum numberof PDCCH candidates and the maximum number of CCEs are larger than thosein case of the [condition A], and thus it is required to drop partialsearch spaces by applying the [Method 1].

At present, the [Method 1] is applied only to the PCell (i.e., in caseof an SCell, it is required to configure the restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs to satisfy the[condition A]), and thus it may be understood that the explanation ofthe present embodiment is restricted to the PCell. However, theexplanation of the present embodiment is not limited thereto, but it canbe further extended to the SCell and PCell.

According to the [Method 1], if the [condition A] is not satisfied at aspecific time (slot), the terminal preferentially selects a commonsearch space among search space sets existing at the corresponding time.If the [condition A] is satisfied even after all the search spacesconfigured as the common search space only are selected, the terminalmay additionally select the search space sets that are configured asUE-specific search spaces. In this case, if there are a plurality ofsearch space sets that are configured as the UE-specific search spaces,the search space set having a low search space set index may have ahigher priority. In consideration of the priority, it is possible toselect the UE-specific search space sets within a range where thecondition A is satisfied.

As described above, individual search spaces are connected to onecontrol resource set (CORESET) and indicated with frequency axisresource information on which the PDCCH can be transmitted and TCI stateinformation (i.e., space related information or QCL information), and incase of the NC-JT for which a plurality transmission points are used ata time, it may be necessary to use one or more pieces of TCI stateinformation at one time (e.g., slot). Considering that one piece of TCIstate information can be allocated (or activated) for one controlresource set, it can be known that, in case of NC-JT transmission, theselected search spaces should be connected to one or more controlresource sets at one time. If the selection of the search space set isdetermined by a single reference (search space set index) as in the[Method 1], it is not guaranteed to satisfy the condition as describedabove, and thus the base station and the terminal can guarantee that atleast one search space for each control resource set (i.e., for eachtransmission point or TRP) is selected at a specific time (slot) withrespect to the terminal to which multi-PDCCH based NC-JT can be appliedthrough the NC-JT related UE capability report or other higher layerconfigurations.

To guarantee that the at least one search space for each controlresource set (i.e., for each transmission point or TRP) is selected atthe specific time (slot) may be performed through various examples asfollows.

-   -   1) If UE-specific search spaces within a specific time (slot)        are connected to control resource sets having two or more        different TCI states during selection of the UE-specific search        spaces at the corresponding time, the terminal should select at        least one search space connected to the second control resource        set. This means that if the UE-specific search spaces within the        corresponding time are connected to the control resource sets        having two or more different TCI states, the selected search        spaces should be connected to the control resource sets having        two or more different TCI states. In this case, it is still        possible to determine the priorities of the respective search        space sets by means of search space set indexes.    -   2) In case of the NC-JT, overbooking of the PDCCH resource        (i.e., the configured restrictions on the maximum number of        PDCCH candidates and the maximum number of CCEs are larger than        those in case of the [condition A], and thus it is required to        drop the partial search spaces) may not be supported. This means        that if the PDCCH resource is overbooked and it is required to        perform search space selection as in the [Method 1], the        terminal does not perform multi-PDCCH reception for the NC-JT.        As another interpretation, if the UE-specific search spaces        selected at the specific time (slot) are connected only to one        CORESET (or only to one TCI state or one TRP), the terminal can        be guaranteed not to perform the multi-PDCCH based NC-JT        operation.    -   3) If the UE-specific search spaces within the specific time        (slot) are connected to two or more control resource sets during        selection of the UE-specific search spaces at the corresponding        time, it is required for the terminal to select at least one        search space connected to the second control resource set. This        may be achieved by a method in which the terminal configures the        priority through a combination with another index, such as a        PDCCH candidate index or control resource set (CORESET) index,        in addition to the search space set index in case that the        UE-specific search spaces within the corresponding time (slot)        are connected to the control resource sets having two or more        different TCI states.

For example, if the UE-specific search spaces within the specific time(slot) are connected to the control resource set(s) having one (or thesame) TCI state, the terminal configures the priority based on thesearch space set index only in the same manner as the [Method 1]. Incontrast, if the UE-specific search spaces within the specific time(slot) are connected to the control resource sets having different TCIstates, the terminal may configure the priorities, such asfirst-order-(PDCCH candidate index #0, search space set index #0),second-order-(PDCCH candidate index #0, search space set index #1),third-order-(PDCCH candidate index #1, search space set index #0),fourth-order-(PDCCH candidate index #1, search space set index #1), andso on, using pairs of a PDCCH candidate index and a search space setindex through the change of the [Method 1]. The above-described methodmay be extended in a similar manner even in case of using pairs of acontrol resource set index and a search space set index, but thedetailed explanation thereof will be omitted.

In this case, it is still possible to determine the priorities ofrespective search space sets by means of search space set indexes.

Third Embodiment: Maximum Spacing Between Monitoring Occasions inConsideration of NC-JT

In the third embodiment, a method for guaranteeing a processing time ofa terminal through restriction of the maximum spacing between monitoringoccasions in consideration of an NC-JT is provided.

FIG. 12 illustrates a diagram of an example of multiplexing controlresource sets in which PDCCHs by TRPs are transmitted during multi-PDCCHbased NC-JT transmission. With reference to FIG. 12, it is possible thatcontrol resource set (CORESET) #1 1210 and 1220 including a PDCCH of thefirst transmission point (TRP) and control resource set (CORESET) #21215 and 1225 including a PDCCH of the second transmission point (TRP)are frequency-division-multiplexed (FDM-multiplexed) using differentfrequency resources at the same time (at least one same OFDM symbol) ina similar manner to the first case 1200, or they are transmitted atdifferent time points (overlapping OFDM symbols do not exist) in asimilar manner to the second case 1205.

The first case 1200 may be used in frequency range 1 (FR1) that is equalto or lower than 6 GHz, in which beams between transmission points maybe equal to each other (or QCL-type-D refers to the same referencesignal), but it may not be easy to apply the first case 1200 infrequency range 2 (FR2) that is higher than 6 GHz, in which there is ahigh probability that the beams between the transmission points aredifferent from each other (or QCL-type-D refers to different referencesignals). Accordingly, it is possible to freely change the beams inaccordance with the change of the transmission points by permittingmonitoring of only PDCCHs transmitted from one transmission point at onetime (OFDM symbol) as in the second case 1205.

In this case, if there is no restriction on a time interval A 1230between the PDCCHs transmitted from the respective transmission points,the terminal is not aware of whether the PDSCH allocated by the firstPDCCH is a PDSCH of a single transmission point (single TRP PDSCH) or aPDSCH of a multi-transmission point (multi-TRP PDSCH or NC-JT PDSCH)before detecting the additional (second) PDCCH in the second controlresource set 1225 after the first PDCCH is detected in the first controlresource set 1220, and thus it may not be possible to sufficientlyprepare for the PDSCH reception. For this, it is possible to set arestriction on the time interval A 1230 required to detect theadditional (second) PDCCH in the second control resource set 1225 afterthe first PDCCH is detected in the first control resource set 1220.

As an example, for the time interval A 1230, it may be engaged that thefirst PDCCH detected in the first control resource set 1220 and thesecond PDCCH detected in the second control resource set 1225 exist inthe same slot. As another example, it may be engaged that the timeinterval A 1230 is defined as a value between the last OFDM symbol inwhich the first PDCCH detected in the first control resource set 1220 istransmitted and the first OFDM symbol in which the second PDCCH detectedin the second control resource set 1225, and the time interval A 1230 issmaller than a predetermined specific value or a specific value beingsignaled to a higher layer. This means that if the second PDCCHallocating the NC-JT PDSCH is not detected after the time interval A1230 after the first PDCCH is detected, the terminal considers the PDSCHallocated by the first PDCCH as a single transmission point PDSCH(single TRP PDSCH) and it perform operations necessary for the PDSCHreception.

Fourth Embodiment: Method for Managing Restrictions on the Maximum PDCCHCandidates and the Maximum Number of CCEs in Consideration of aCombination of CA or DC with NC-JT

In the fourth embodiment, methods for managing restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs inconsideration of a case where a CA or a DC and an NC-JT are operatedtogether are provided.

A base station may configure a terminal having reported that a DCoperation is possible through a UE capability report to perform the DCoperation. Only the terminal that reports that the DC operation ispossible through the UE capability report may reportpdcch-BlindDetectionMCG-UE and pdcch-BlindDetectionSCG-UE, which arePDCCH monitoring UE capability reports for a master cell group (MCG) anda secondary cell group (SCG). In this case, the value ofpdcch-BlindDetectionMCG-UE or pdcch-BlindDetectionSCG-UE is one of [1, .. . , pdcch-BlindDetectionCA-1], and the sum of the values ofpdcch-BlindDetectionMCG-UE and pdcch-BlindDetectionSCG-UE should beequal to or larger than the value of pdcch-BlindDetectionCA. This is toguarantee the degree of freedom of scheduling of the base station.

If the terminal is configured not to perform the DC operation, theterminal may determine the number N^(cap) of downlink cells capable ofmonitoring PDCCH candidates through one of the methods of theembodiments 1 to 3 (The terminal may determine the number of downlinkcells being considered during monitoring of the PDCCH candidates in thesame method. That is, the terminal may calculate the maximum PDCCHdetection complexity by multiplying the values of the table 10 or thetable 11 by N^(cap). The above-described methods may be applied to thecase where the number N^(cap) of downlink cells described in thedisclosure is determined) in all.

As an example, if a certain terminal reports that the terminal canperform carrier aggregation for 5 or more serving cells to the basestation through UE-NR-Capability, the terminal should also reportpdcch-BlindDetectionCA that is a UE capability report for the PDCCHmonitoring for the carrier aggregation. In this case, as described abovein the embodiments 1 to 3, the number N^(cap) of downlink cells capableof monitoring the PDCCH candidates follows the value ofpdcch-BlindDetectionCA that is the UE capability report.

In contrast, if a certain terminal reports that the terminal can performcarrier aggregation for 4 or less serving cells to the base stationthrough UE-NR-Capability, the terminal may omit pdcch-BlindDetectionCAthat is the UE capability report for the PDCCH monitoring, and in thiscase, the number N^(cap) of downlink cells capable of monitoring thePDCCH candidates follows the number of downlink cells configured to thecorresponding terminal.

If the terminal is configured to perform the DC operation with respectto the maximum number N_(DC) of downlink cells, the base stationconfigures pdcch-BlindDetectionMCG that is a parameter for an MCG andpdcch-BlindDetectionSCG that is a parameter for an SCG to the terminal.In this case, it is required for the base station to guarantee that thesum of values of the two parameters pdcch-BlindDetectionMCG andpdcch-BlindDetectionSCG is equal to or smaller than the value ofpdcch-BlindDetectionCA with respect to the terminal having reported thepdcch-BlindDetectionCA (i.e., the terminal supporting the carrieraggregation or DC for 5 or more downlink cells). Further, if theterminal omits the report for pdcch-BlindDetectionCA (i.e., with respectto the terminal supporting the carrier aggregation or DC for 4 or lessdownlink cells), it is required for the base station to guarantee thatthe sum of values of the two parameters pdcch-BlindDetectionMCG andpdcch-BlindDetectionSCG is equal to or smaller than the configuredmaximum number N_(DC) of DC downlink cells. This is to guarantee themaximum PDCCH detection complexity of the terminal to be equal to orlower than a predetermined level. In this case, the terminal assumesthat the number N^(cap) of downlink cells capable of monitoring thePDCCH candidates in the MCG is pdcch-BlindDetectionMCG, and it assumesthat the number N^(cap) of downlink cells capable of monitoring thePDCCH candidates in the SCG is pdcch-BlindDetectionSCG.

If the terminal omits the report for pdcch-BlindDetectionCA, andN_(DCmax) is the maximum number of downlink cells that can be configuredthrough both the MCG and the SCG, the values ofpdcch-BlindDetectionMCG-UE and pdcch-BlindDetectionSCG-UE may be one of[1, 2, 3]. Further, the sum of the values of pdcch-BlindDetectionMCG-UEand pdcch-BlindDetectionSCG-UE should be equal to or larger thanN_(DCmax).

For the NC-JT, it is possible for the base station to allocate aplurality of PDSCHs in the same cell and bandwidth part to the terminalthrough a plurality of PDCCHs. If the base station determines therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs using only [condition A], [first restriction], and[second restriction] as described above in a situation where the basestation operates the NC-JT and the carrier aggregation or the DC at thesame time, the plurality of PDCCHs for the NC-JT should be transmittedwithin the restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs, such as the plurality of PDCCHs for thecarrier aggregation, and thus the degree of freedom of PDCCHtransmission for the existing carrier aggregation is unable to bemaintained.

To solve this, it is possible to introduce “UE capability report foradditional PDCCH candidate monitoring” in addition to the UE capabilityreport for the number of downlink cells capable of monitoring the PDCCHcandidates, and thus to extend the restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs. The UE capabilityreport for the additional PDCCH candidate monitoring may be notificationof whether carrier aggregation, the DC, and separate additional PDCCHcandidate monitoring are possible or the degree of the additional PDCCHcandidate monitoring through additional signaling, for example, throughpdcch-BlindDetectionNCJT signaling of one or more bits in addition topdcch-BlindDetectionCA, pdcch-BlindDetectionMCG-UE, andpdcch-BlindDetectionSCG-UE that are the UE capability reports for thePDCCH monitoring for the carrier aggregation. Thepdcch-BlindDetectionNCJT is an inscription for discriminating the UEcapability report or signaling configured by the base station, and itmay be replaced by various expressions, such as pdcch-BlindDetectionCoMPand so on, during an actual application thereof, but for convenience inthe following explanation, it is standardized aspdcch-BlindDetectionNCJT.

The above explanation means that it is possible to extend therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs, if needed, even in case that the maximum number ofdownlink cells configured to the terminal for the CA or the DC is notsufficiently large (e.g., is not larger than N^(cap)). Specifically, thebase station can extend the restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs through the following methodsonly with respect to the terminal having performed the UE capabilityreport for the additional PDCCH candidate monitoring among the terminalssupporting the NC-JT.

[Method A]

According to [Method A], if corresponding signaling exists (e.g., ifpdcch-BlindDetectionNCJT is reported to the base station) through the UEcapability report for the additional PDCCH candidate monitoring, therestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs in the related art are increased in a specific ratio(e.g., twice or multiple of the configured number of TRPs, the number ofCORESET groups, and the number of PUCCH resource sets/groups). In thepresent embodiment, it may be understood that the number N^(cap) ofdownlink cells for the PDCCH candidate monitoring in accordance withrespective cases is increased in the specific ratio (e.g., twice). Thespecific ratio may be one of a predetermined value in accordance withthe kind of the UE capability report for the additional PDCCH candidatemonitoring and a value indicated through higher layer signaling. It ispossible to engage for the UE capability report for the additional PDCCHcandidate monitoring so that a single value is applied to all the cells,or separate values are applied by frequency bands (e.g., frequency range1 equal to or lower than 6 GHz versus frequency range 2 higher than 6GHz), or separate values are applied by numerology/subcarrier spacing(SCS), or separate values are applied by cell groups/cells/bandwidthparts. Hereinafter, an example of a change of restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs by[Method A] will be described.

Case #1 (≤N^(cap) DL cells+non-DC+non-NCJT): If the terminal isconfigured with N^(cap) or less downlink cells with respect to possiblesubcarrier spacing μ=0, 1, 2, 3, and is not configured with an NR-DCoperation, and does not report the UE capability report for additionalPDCCH candidates monitoring (pdcch-BlindDetectionNCJT-UE) to the basestation (or the base station does not configure the additional PDCCHcandidate monitoring pdcch-BlindDetectionNCJT), restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs forone downlink cell in one slot follow M^(μ) of the table 10 and C^(μ) ofthe table 11.

Case #2 (>N^(cap) DL cells+non-DC+non-NCJT): If the terminal isconfigured with more than N^(cap) downlink cells with respect topossible subcarrier spacing μ=0, 1, 2, 3, and is not configured with anNR-DC operation, and reports the UE capability reportpdcch-BlindDetectionCA-UE for PDCCH monitoring for carrier aggregationto the base station, and does not report the UE capability reportpdcch-BlindDetectionNCJT-UE for additional PDCCH candidate monitoring tothe base station (or the base station does not configure the additionalPDCCH candidate monitoring pdcch-BlindDetectionNCJT), restrictions onthe maximum number of PDCCH candidates and the maximum number of CCEs inone slot follow the mathematical expression 1 and the mathematicalexpression 2. This is the same as the case where the number N^(cap) ofdownlink cells capable of monitoring the PDCCH candidates follows thevalue of pdcch-BlindDetectionCA that is the UE capability report.

Case #3 (≤N^(cap) DL cells+non-DC+NCJT): If the terminal is configuredwith N^(cap) or less downlink cells with respect to possible subcarrierspacing μ=0, 1, 2, 3, and is not configured with an NR-DC operation, andreports the UE capability report for additional PDCCH candidatemonitoring (pdcch-BlindDetectionNCJT-UE) to the base station (or thebase station configures the additional PDCCH candidate monitoring(pdcch-BlindDetectionNCJT)), restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs for one downlink cell in oneslot follow X times (e.g., X=2) M^(μ) of the table 10 and C^(μ) of thetable 11.

This means that the values of M^(μ) or C^(μ) that are the restrictionson the maximum number of PDCCH candidates and the maximum number of CCEsfor each cell in min(M^(μ), M^(total,μ)) and min(C^(μ), C^(total,μ)) ofthe second restriction can be increased to be equal to or larger thanthe values of the tables 10 and 11 by the base station configuration orthe UE capability report. In this case, the terminal may consider asmaller one of value A (product of the X, the configured number ofdownlink cells, and M^(μ) of the table 10 or C^(μ) of the table 11) andvalue B (value of 4*M^(μ) or 4*C^(μ)) as the restriction of the maximumnumber of PDCCH candidates and the maximum number of CCEs. This is toguarantee that additional PDCCH candidate monitoring for the NC-JT isperformed within the maximum PDCCH detection complexity for performingthe CA.

Case #4 (>N^(cap) DL cells+non-DC+NCJT): If the terminal is configuredwith more than N^(cap) downlink cells with respect to possiblesubcarrier spacing μ=0, 1, 2, 3, and is not configured with an NR-DCoperation, and reports the UE capability report pdcch-BlindDetectionCAfor PDCCH monitoring for carrier aggregation to the base station, andreports the UE capability report for additional PDCCH candidatemonitoring (pdcch-BlindDetectionNCJT-UE) to the base station (or thebase station configures the additional PDCCH candidate monitoringpdcch-BlindDetectionNCJT), restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs in one slot follow X times(e.g., X=2) the mathematical expression 1 and the mathematicalexpression 2. This may be understood that N^(cap) is multiplied by X(e.g., X=2) to be applied in the mathematical expression 1 and themathematical expression 2.

Case #5 (≤N^(cap) DL cells+DC+non-NCJT): If the terminal is configuredwith an NR-DC operation, and is configured with N^(cap) or less downlinkcells with respect to possible subcarrier spacing μ=0, 1, 2, 3 in thecorresponding MCG or SCG, and does not report the UE capability reportUE capability report for additional PDCCH candidate monitoring(pdcch-BlindDetectionNCJT-UE) to the base station (or the base stationdoes not configure the additional PDCCH candidate monitoringpdcch-BlindDetectionNCJT), restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs for one downlink cell in oneslot follow M^(μ) of the table 10 and C^(μ) of the table 11. In thiscase, as described above, the N^(cap) is determined bypdcch-BlindDetectionMCG or pdcch-BlindDetectionSCG.

Case #6 (>N^(cap) DL cells+DC+non-NCJT): If the terminal is configuredwith an NR-DC operation, and is configured with more than N^(cap)downlink cells with respect to possible subcarrier spacing μ=0, 1, 2, 3in the corresponding MCG or SCG, and does not report the UE capabilityreport pdcch-BlindDetectionNCJT-UE for additional PDCCH candidatemonitoring to the base station (or the base station does not configurethe additional PDCCH candidate monitoring pdcch-BlindDetectionNCJT),restrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs in one slot follow the mathematical expression 1 and themathematical expression 2. In this case, as described above, the N^(cap)is determined by pdcch-BlindDetectionMCG or pdcch-BlindDetectionSCG.

Case #7 (≤N^(cap) DL cells+DC+NCJT): If the terminal is configured withan NR-DC operation, and is configured with Ncap or less downlink cellswith respect to possible subcarrier spacing μ=0, 1, 2, 3 in thecorresponding MCG or SCG, and reports the UE capability report foradditional PDCCH candidate monitoring (pdcch-BlindDetectionNCJT-UE) tothe base station (or the base station configures the additional PDCCHcandidate monitoring (pdcch-BlindDetectionNCJT), restrictions on themaximum number of PDCCH candidates and the maximum number of CCEs forone downlink cell in one slot follow X times (e.g., X=2) M^(μ) of thetable 10 and C^(μ) of the table 11.

This means that the values of M^(μ) or C^(μ) that are the restrictionson the maximum number of PDCCH candidates and the maximum number of CCEsfor each cell in min(M^(μ), M^(total,μ)) and min(C^(μ), C^(total,μ)) ofthe second restriction can be increased to be equal to or larger thanthe values of the tables 10 and 11 by the base station configuration orthe UE capability report. In this case, the terminal may consider asmaller one of value A (product of the X, the configured number ofdownlink cells, and M^(μ) of the table 10 or C^(μ) of the table 11) andvalue B (value of 4*M^(μ) or 4*C^(μ)) as the restriction of the maximumnumber of PDCCH candidates and the maximum number of CCEs. This is toguarantee that additional PDCCH candidate monitoring for the NC-JT isperformed within the maximum PDCCH detection complexity for performingthe DC. In this case, as described above, the N^(cap) is determined bypdcch-BlindDetectionMCG or pdcch-BlindDetectionSCG.

Case #8 (>N^(cap) DL cells+DC+NCJT): If the terminal is configured withan NR-DC operation, and is configured with more than N^(cap) downlinkcells with respect to possible subcarrier spacing μ=0, 1, 2, 3 in thecorresponding MCG or SCG, and reports the UE capability report foradditional PDCCH candidate monitoring (pdcch-BlindDetectionNCJT-UE) tothe base station for additional PDCCH candidate monitoring to the basestation (or the base station configures the additional PDCCH candidatemonitoring pdcch-BlindDetectionNCJT), restrictions on the maximum numberof PDCCH candidates and the maximum number of CCEs in one slot follow Xtimes (e.g., X=2) the mathematical expression 1 and the mathematicalexpression 2. This may be understood that N^(cap) is multiplied by X(e.g., X=2) to be applied in the mathematical expression 1 and themathematical expression 2. This means that the values of M^(μ) or C^(μ)that are the restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs for each cell in min(M^(μ),M^(total,μ)) andmin(C^(μ),C^(total,μ)) of the second restriction can be increased to beequal to or larger than the values of the tables 10 and 11 by the basestation configuration or the UE capability report. In this case, asdescribed above, the N^(cap) is determined by pdcch-BlindDetectionMCG orpdcch-BlindDetectionSCG.

In addition to the above-described example, various modifications arepossible, but are not enumerated herein in order to avoid obscuring ofthe gist of the explanation.

[Method B]

According to [Method B], if corresponding signaling exists (e.g., ifpdcch-BlindDetectionNCJT is reported to the base station), the conditionto control the restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs in the related art is extended throughthe UE capability report for the additional PDCCH candidate monitoring.It is possible to engage for the UE capability report for the additionalPDCCH candidate monitoring so that a single value is applied to all thecells, or separate values are applied by frequency bands (e.g.,frequency range 1 equal to or lower than 6 GHz versus frequency range 2higher than 6 GHz), or separate values are applied bynumerology/subcarrier spacing (SCS), or separate values are applied bycell groups/cells/bandwidth parts. As an example, if at least onecondition is satisfied between condition 1) on which the terminal isconfigured with more than N^(cap) downlink cells with respect topossible subcarrier spacing μ=0, 1, 2, 3, and condition 2) on which theterminal reports the UE capability report pdcch-BlindDetectionNCJT foradditional PDCCH candidate monitoring to the base station, it ispossible to engage for the extension of the restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs of theterminal. This is to guarantee that the terminals that should detect aplurality of pieces of DCI in one cell for the NC-JT operation canperform the additional PDCCH candidate monitoring even if the configurednumber of downlink cells is smaller than N^(C)W. An example of a changeof the restrictions on the maximum number of PDCCH candidates and themaximum number of CCEs by [Method B] will be described.

Case #1: If the terminal is configured with N^(cap) or less downlinkcells with respect to possible subcarrier spacing μ = 0, 1, 2, 3, anddoes not report the UE capability report pdcch-BlindDetectionNCIT foradditional PDCCH candidate monitoring to the base station, restrictionson the maximum number of PDCCH candidates and the maximum number of CCEsfor one downlink cell in one slot follow M^(μ) of the table 10 and C^(μ)of the table 11. Case #2: If the terminal is configured with more thanN^(cap) downlink cells with respect to possible subcarrier spacing μ =0, 1, 2, 3, or the terminal reports the UE capability reportpdcch-BlindDetectionNCIT for additional PDCCH candidate monitoring tothe base station, restrictions on the maximum number of PDCCH candidatesand the maximum number of CCEs follow mathematical expression 10 andmathematical expression 11 below. [Mathematical expression 10]M^(total,μ) = └ N^(cap) · M^(μ) · N^(μ)/N^(total) ┘ [Mathematicalexpression 11] M^(total,μ) = └ N^(cap) · C^(μ) · N^(μ)/N^(total) ┘

In addition to the above-described example, various modifications arepossible, but are not enumerated herein in order to avoid obscuring ofthe gist of the explanation.

[Method C]

According to [Method C], if corresponding signaling exists (e.g., ifpdcch-BlindDetectionNCJT is reported to the base station), thedefinition of the number of downlink cells configured to the terminal inthe related art is changed through the UE capability report for theadditional PDCCH candidate monitoring. It is possible to engage for theUE capability report for the additional PDCCH candidate monitoring sothat a single value is applied to all the cells, or separate values areapplied by frequency bands (e.g., frequency range 1 equal to or lowerthan 6 GHz versus frequency range 2 higher than 6 GHz), or separatevalues are applied by numerologies/subcarrier spacing (SCS), or separatevalues are applied by cell groups/cells/bandwidth parts. This is toguarantee that the terminals that should detect a plurality of pieces ofDCI in one cell for the NC-JT operation can perform the additional PDCCHcandidate monitoring even if the configured number of downlink cells issmaller than N^(cap).

As an example, if the UE capability report for the additional PDCCHcandidate monitoring or signaling on whether to apply the NC-JT isapplied to all the cells, the terminal multiplies the configured numberof downlink cells by the number of PDSCHs for the NC-JT (or the numberof codewords or a value that is signaled or reported by the terminal),and if the value is larger than a specific value (e.g., if the NR-DCoperation is not configured, the value is 4, whereas if the NR-DCoperation is configured, the value is N^(cap)), it is possible to engagefor the extension of the restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs.

As another example, if the UE capability report (e.g.,pdcch-BlindDetectionNCJT-UE) for the additional candidate monitoring orsignaling on whether to apply the NC-JT configured by the base station(e.g., pdcch-BlindDetectionNCJT) is reported and applied by downlinkcells, the terminal may count a number of a downlink cells to which theNC-JT is applied as X when calculating the configured number of thecorresponding cells. Here, X may be various values, such as theconfigured number of TRPs, the number of CORESET groups, or the numberof PUCCH resource sets/groups.

For example, if the terminal is configured with 3 downlink cells intotal, and additional PDCCH candidate monitoring for the NC-JT isapplied to 2 of the 3 downlink cells and the additional PDCCH candidatemonitoring is not applied to one remaining cell, it may be assumed thatthe terminal counts 4 by multiplying the 2 cells by 2, and counts 1without multiplying the one cell by 2 to configure total 5 downlinkcells. This may be understood that the configured number N^(μ) orN^(total) of downlink cells as described above is calculated, and N^(μ)is multiplied by a coefficient X_(i) in a comparison process with thevalue N^(cap). As an example, i may be one of a serving cell ID, SCS,BWP ID, cell group ID, CORESET ID, CORESET group ID, and PUCCHresource/set/group ID. It is possible to insert IDs of the serving cellID, SCS, BWP ID, cell group ID, and CORESET group ID in the mathematicalexpressions 1 to 11 in order to indicate whether to apply the additionalPDCCH candidate monitoring with respect to the group represented by thecorresponding IDs. As an example, if it is assumed that i is a cell ID,X_(i) becomes 1 with respect to the cell to which the additional PDCCHcandidate monitoring is not applied, whereas it becomes a value that islarger than 1 (e.g., 2) with respect to the cell to which the additionalPDCCH candidate monitoring is applied, so that it can exert an influenceon the determination of the value of M^(total) or C^(total) in themathematical expressions 1 to 11.

According to the present embodiment, it is possible to change or/andextend the second restriction as follows. UE capability report signalingon whether the additional PDCCH candidate monitoring is possible iscalled pdcch-BlindDetectionNCJT-UE, and signaling on whether to applythe additional PDCCH candidate monitoring configured by the base stationis called pdcch-BlindDetectionNCJT. Based on M^(μ) of the table 10 andC^(μ) of the table 11, the terminal is not required to monitor PDCCHcandidates the number of which is larger thanmin(X_(i)*M^(μ),M^(total,μ)) (or min(X_(i)+M^(μ),M^(total,μ))) or tomonitor CCEs the number of which is larger thanmin(X_(i)*C^(μ),C^(total,μ)) (or min(X_(i)+C^(μ),C^(total,μ))) withrespect to activated bandwidth parts configured with the subcarrierspacing p in the individually scheduled cells. In this case, values ofM^(total,μ) and C^(total,μ) may be increased in accordance withpdcch-BlindDetectionNCJT configured by the base station, and values ofX_(i)*M^(μ) and X_(i)*C^(μ) (or X_(i)+M^(μ) and X_(i)+C^(μ)) may berestricted/increased in accordance with the UE capability reportsignaling pdcch-BlindDetectionNCJT-UE. This is called a corrected secondrestriction. That is, the corrected second restriction may call a changeof the maximum PDCCH candidates and the maximum number of CCEs that canbe applied to a specific cell configured with the subcarrier spacing pin accordance with the UE capability report or base stationconfiguration.

In configuring a search space set for a specific cell PCell, the basestation may notify the terminal of configurations including PDCCHcandidates or CCEs the number of which is larger than M^(μ) of the table10 and C^(μ) of the table 11 which do not satisfy the above-describedcondition A. If the search space of the specific cell exceeds thecorrected second restriction when the terminal monitors the search spaceof the specific cell at a specific time in accordance with the searchspace configuration of the base station, the terminal may selectivelymonitor a specific search space set in the procedure of the [Method 1]as described above.

Table 16 below presents an example of a change of the restrictions onthe maximum number of PDCCH candidates and the maximum number of CCEs by[Method C].

TABLE 16 If the terminal is configured with N^(cap) or less downlinkcells with respect to possible subcarrier spacing μ = 0, 1, 2, 3,restrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs in one slot and in one downlink cell follow M^(μ) of thetable 10 and C^(μ) of the table 11.${{If}\mspace{14mu} a\mspace{14mu}{condition}\mspace{14mu}{\sum\limits_{\mu = 0}^{3}\;{X \cdot N^{\mu}}}} \leq {N^{cap}\mspace{14mu}\left( {{e.g.},{X > 1},{here},{{it}\mspace{14mu}{is}\mspace{14mu}{possible}\mspace{14mu}{that}\mspace{14mu} X\mspace{14mu}{has}\mspace{14mu} a\mspace{14mu}{different}}} \right.}$value for each μ or for each cell) is satisfied by the number ofdownlink cells with which the terminal is configured with respect topossible subcarrier spacing μ = 0, 1, 2, 3 and the UE capability reportpdcch-BlindDetectionNCJT for the additional PDCCH candidate monitoring,restrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs in one slot and in one downlink cell follow M^(μ) of thetable 10 and C^(μ) of the table 11. If the terminal is configured withmore than N^(cap) downlink cells with respect to possible subcarrierspacing μ = 0, 1, 2, 3, or reports the UE capability report pdcch-BlindDetectionNCJT for additional PDCCH candidate monitoring to the basestation, restrictions on the maximum number of PDCCH candidates and themaximum number of CCEs in one slot follow mathematical expression 10 andmathematical expression 11.${{If}\mspace{14mu} a\mspace{14mu}{condition}\mspace{14mu}{\sum\limits_{\mu = 0}^{3}\;{X \cdot N^{\mu}}}} > {N^{cap}\mspace{14mu}\left( {{e.g.},{X > 1},{here},{{it}\mspace{14mu}{is}\mspace{14mu}{possible}\mspace{14mu}{that}\mspace{14mu} X\mspace{14mu}{has}\mspace{14mu} a\mspace{14mu}{different}}} \right.}$value for each μ or for each cell) is satisfied by the number ofdownlink cells with which the terminal is configured with respect topossible subcarrier spacing μ = 0, 1, 2, 3 and the UE capability reportpdcch-BlindDetectionNCJT for the additional PDCCH candidate monitoring,restrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs follow the mathematical expression 10 and themathematical expression 11.

In addition to the table 16, various modifications are possible, but arenot enumerated herein in order to avoid obscuring of the gist of theexplanation.

It is possible to differently apply the restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs by [Method A]to [Method C] by frequency bands (e.g., frequency range 1 equal to orlower than 6 GHz versus frequency range 2 higher than 6 GHz).

In the present embodiment, [Method A] to [Method C] are not exclusive toeach other, but can be combined and applied together. For example,[Method C] may be applied in consideration of the mathematicalexpressions 3 and 4 in [Method A].

Hereinafter, for convenience in explanation, the restriction on themaximum number of PDCCH candidates and the maximum number of CCEs by[Method A] to [Method C] may be called a third restriction.

FIG. 13 illustrates a diagram of an operation of a terminal to determinerestrictions on the maximum number of PDCCH candidates and the maximumnumber of CCEs according to an embodiment of the disclosure. Atoperation 1300, with respect to a base station, the terminal performs aUE capability report (e.g. pdcch-BlindDetectionCA) for PDCCH monitoringfor carrier aggregation and a UE capability report (e.g.pdcch-BlindDetectionNCJT) notifying whether additional PDCCH candidatemonitoring is possible and the degree of the additional PDCCH candidatemonitoring. At operation 1305, the base station performs higher layerconfigurations for downlink cells for carrier aggregation, whether anNC-JT transmission is possible, or whether multi-PDCCH based NC-JTtransmission is possible based on the UE capability reports. Thereafter,the base station and the terminal determine whether additional PDCCHblind decoding for CA is possible by the UE capability report andsubsequent higher layer configuration values (1310).

If the additional PDCCH blind decoding is not possible, the terminalperforms PDCCH blind decoding in accordance with the [condition A](1320). In contrast, if the additional PDCCH blind decoding is possible,the terminal additionally determines whether additional PDCCH blinddecoding for an NC-JT is possible (1315), and if the additional PDCCHblind decoding for the NC-JT is not possible, the terminal determineswhether the number of downlink cells configured for the carrieraggregation is larger than 4 (1330). In accordance with the result ofthe determination, the terminal may perform PDCCH decoding withoutchanging restrictions on the maximum number of PDCCH candidates and themaximum number of CCEs (1320), or the terminal may perform the PDCCHdecoding by increasing the restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs, that is, in accordance with afirst restriction and a second restriction (1340).

If the terminal determines that the additional PDCCH blind decoding forthe NC-JT is possible, the terminal may additionally determine whetherthe third restriction is applicable in accordance with theabove-described method (e.g., depending on whether the maximum number ofPDSCHs configured for the CA and NC-JT is equal to or larger than aspecific value (1335), and in accordance with the result of thedetermination, the terminal may perform the PDCCH decoding withoutchanging the restrictions on the maximum number of PDCCH candidates andthe maximum number of CCEs (1320), or the terminal may perform the PDCCHdecoding in accordance with the third restriction and the secondrestriction by additionally increasing the restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs (1335).

Further, the contents of FIG. 13 are applied to the base station, andthe base station may determine the restrictions on the maximum number ofPDCCH candidates and the maximum number of CCEs of the terminal inaccordance with the contents of FIG. 13.

As described above, for the NC-JT operation, the base station may assigntwo or more PDSCHs to the same terminal in the same cell and in the samebandwidth part in a manner that it selects one of 1) transmission of aplurality of PDCCHs allocating different PDSCHs and 2) allocation of aplurality of PDSCHs on one PDCCH. In this case, if the base stationselects the second method, that is, allocation of the plurality ofPDSCHs on one PDCCH, the number of PDCCHs is not increased even if theNC-JT operation is performed, and thus it is possible not to apply themethods for increasing the PDCCH candidate monitoring as described abovein the above examples.

If the allocation of the plurality of PDSCHs on one PDCCH is selected,it is to be noted that two or more TCI states areconfigured/allocated/activated at one TCI code point, and thus it ispossible for the terminal to engage for non-performing of the multi-DCINC-JT PDCCH blind decoding operation or the multi-DCI NC-JT PDSCHreception operation in case that two or more TCI states are configured,allocated, or activated at one TCI code point. Through this, it ispossible to avoid unnecessary PDCCH detection complexity improvement ofthe terminal.

In the above-described embodiments, the methods for increasing themaximum number of PDCCH candidate BDs/CCEs in one cell in accordancewith the NC-JT application, but it is not necessary to restrict theusage of the methods depending on whether to apply the NC-JT. Forexample, in case of the terminals simultaneously supporting variousverticals, such as eMBB, URLLC, and so on, it is necessary to increasethe degree of freedom of PDCCH transmission by increasing the additionalPDCCH candidate and CCE detection complexity at the specific time, andfor this, the above-described embodiments can be properly adopted.

In order to perform the above-described embodiments of the disclosure,transmitters, receivers, and processors of a terminal and a base stationare illustrated in FIGS. 14 and 15. In the 5G communication systemcorresponding to the above-described embodiments, the transmission andreception method of the base station and the terminal for adopting themethod for transmitting and receiving the downlink control channel andthe downlink control information has been described, and in order toperform this, the transmitters, receivers, and processors of the basestation and the terminal should operate in accordance with therespective embodiments.

Specifically, FIG. 14 illustrates a block diagram of the internalconfiguration of a terminal according to an embodiment of thedisclosure. As illustrated in FIG. 14, a terminal according to thedisclosure may include a terminal processor 1400, a receiver 1410, and atransmitter 1420.

The terminal processor 1400 may control a series of processes in whichthe terminal can operate according to an embodiment of the disclosure.For example, the terminal processor 1400 may differently control themethod for calculating the restrictions on the maximum number of PDCCHcandidates and the maximum number of CCEs and the PDCCH monitoringoperation of the terminal according to an embodiment of the disclosure.In an embodiment of the disclosure, the terminal receiver 1410 and theterminal transmitter 1420 may be commonly called a transceiver. Thetransceiver may transmit/receive a signal to/from a base station. Thesignal may include control information and data. For this, thetransceiver may include an RF transmitter up-converting and amplifying afrequency of a transmitted signal, and an RF receiverlow-noise-amplifying the received signal and down-converting thefrequency of the amplified signal. Further, the transceiver of theterminal may receive the signal through a radio channel, output thesignal to the terminal processor 1400, and transmit the signal outputfrom the terminal processor 1400 through the radio channel.

FIG. 15 illustrates a block diagram of the internal configuration of abase station according to the embodiments of the disclosure. Asillustrated in FIG. 15, a base station according to the disclosure mayinclude a base station processor 1500, a receiver 1510, and atransmitter 1520.

The base station processor 1500 may control a series of processes inwhich the base station can operate according to an embodiment of thedisclosure. For example, the base station processor 1500 may differentlycontrol the method for calculating the restrictions on the maximumnumber of PDCCH candidates and the maximum number of CCEs and thecontrol resource set and search space configuration operation of thebase station. In an embodiment of the disclosure, the base stationreceiver 1510 and the base station transmitter 1520 may be commonlycalled a transceiver. The transceiver may transmit/receive a signalto/from a terminal. The signal may include control information and data.For this, the transceiver may include an RF transmitter up-convertingand amplifying a frequency of a transmitted signal, and an RF receiverlow-noise-amplifying the received signal and down-converting thefrequency of the amplified signal. Further, the transceiver may receivethe signal through a radio channel, output the signal to the basestation processor 1500, and transmit the signal output from the basestation processor 1500 through the radio channel.

Although preferred embodiments of the disclosure have been described inthe specification and drawings and specific wordings have been used,these are merely used as general meanings to assist those of ordinaryskill in the art to gain a comprehensive understanding of thedisclosure, and do not limit the scope of the disclosure. It will beapparent to those of ordinary skill in the art to which the disclosurepertains that various modifications are possible on the basis of thetechnical concept of the disclosure in addition to the embodimentsdisclosed herein. Further, if needed, the respective embodiments may becombined and operated with each other.

Although the present disclosure has been described with variousembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a terminal in acommunication system, the method comprising: identifying a number ofcells associated with a capability to monitor physical downlink controlchannel (PDCCH) candidates based on a number of cells in a first set anda product of a number of cells in a second set and a coefficient;determining a maximum number of PDCCH candidates for each cell based onthe number of cells associated with the capability to monitor PDCCHcandidates; identifying search spaces to monitor based on the maximumnumber of PDCCH candidates; and monitoring a PDCCH on the identifiedsearch space.
 2. The method of claim 1, wherein the maximum number ofPDCCH candidates is determined based on whether the number of cellsassociated with the capability to monitor PDCCH candidates is equal toor less than a number of configured cells which is determined based on acontrol resource set (CORESET) group identifier configured to each cellor not.
 3. The method of claim 2, wherein in case that the number ofcells associated with the capability to monitor PDCCH candidates isequal to or less than the number of configured cells, the maximum numberof PDCCH candidates for a cell is determined as a preconfigured maximumnumber of monitored PDCCH candidates corresponding to a subcarrierspacing of the cell or a multiple of the preconfigured number ofmonitored PDCCH candidates corresponding to a subcarrier spacing of thecell based on the CORESET group identifier configured to the cell. 4.The method of claim 2, wherein in case that the number of cells is notequal to or less than the number of configured cells, the maximum numberof PDCCH candidates for a cell is determined based on a numberM^(total,μ) corresponding to following equation:M ^(total,μ) =└N ^(cap) ×M ^(μ) ×N ^(μ) /N ^(total)┘, where N^(cap) isthe number of cells associated with the capability to monitor PDCCHcandidates, M^(μ) is a preconfigured maximum number of monitored PDCCHcandidates corresponding to a subcarrier spacing of the cell μ, N^(μ) isa number of at least one configured cells corresponding to thesubcarrier spacing of the cell μ determined based on the CORESET groupidentifier configured to the cell, and N^(total) is the number ofconfigured cells.
 5. The method of claim 1, wherein the coefficient isassociated with a CORESET group identifier configured to each of thecell in the second set.
 6. The method of claim 5, wherein theidentifying the search spaces comprises: selecting a search space tomonitor which corresponds to CORESETs of a first CORESET groupidentifier (ID) in case that it is needed to select the search space tomonitor in a primary cell.
 7. A method performed by a base station in acommunication system, the method comprising: identifying a number ofcells associated with a capability to monitor physical downlink controlchannel (PDCCH) candidates of a terminal based on a number of cells in afirst set and a product of a number of cells in a second set and acoefficient; determining a maximum number of PDCCH candidates for eachcell based on the number of cells associated with the capability tomonitor PDCCH candidates; identifying search spaces to be monitored bythe terminal based on the maximum number of PDCCH candidates; andtransmitting downlink control information on the identified search spaceof a PDCCH.
 8. The method of claim 7, wherein the maximum number ofPDCCH candidates is determined based on whether the number of cellsassociated with the capability to monitor PDCCH candidates is equal toor less than a second number of configured cells which is determinedbased on a control resource set (CORESET) group identifier configured toeach cell or not.
 9. The method of claim 8, wherein in case that thenumber of cells associated with the capability to monitor PDCCHcandidates is equal to or less than the second number of configuredcells, the maximum number of PDCCH candidates for a cell is determinedas a preconfigured maximum number of monitored PDCCH candidatescorresponding to a subcarrier spacing of the cell or a multiple of thepreconfigured maximum number of monitored PDCCH candidates correspondingto a subcarrier spacing of the cell based on the CORESET groupidentifier configured to the cell.
 10. The method of claim 8, wherein incase that the number of cells associated with the capability to monitorPDCCH candidates is not equal to or less than the number of configuredcells, the maximum number of PDCCH candidates for a cell is determinedbased on a number M^(total,μ) corresponding to following equation:M ^(total,μ) =└N ^(cap) ×M ^(μ) ×N ^(μ) /N ^(total)┘, where N^(cap) isthe number of cells associated with the capability to monitor PDCCHcandidates, M^(μ) is a preconfigured maximum number of monitored PDCCHcandidates corresponding to a subcarrier spacing of the cell μ, N^(μ) isa number of at least one configured cells corresponding to thesubcarrier spacing of the cell μ determined based on the CORESET groupidentifier configured to the cell, and N^(total) is the second number ofconfigured cells.
 11. The method of claim 7, wherein the coefficient isassociated with a CORESET group identifier configured to each of thecell in the second set.
 12. The method of claim 11, wherein theidentifying the search spaces comprises: selecting a search space to bemonitored which corresponds to CORESETs of a first CORESET groupidentifier (ID) in case that it is needed to select the search space tomonitor in a primary cell.
 13. A terminal in a communication system, theterminal comprising: a transceiver; and a controller coupled with thetransceiver and configured to: identify a number of cells associatedwith a capability to monitor physical downlink control channel (PDCCH)candidates based on a number of cells in a first set and a product of anumber of cells in a second set and a coefficient, determine a maximumnumber of PDCCH candidates for each cell based on the number of cellsassociated with the capability to monitor PDCCH candidates, identifysearch spaces to monitor based on the maximum number of PDCCHcandidates, and perform monitoring a PDCCH on the identified searchspace.
 14. The terminal of claim 13, wherein the maximum number of PDCCHcandidates is determined based on whether the number of cells associatedwith the capability to monitor PDCCH candidates is equal to or less thana number of configured cells which is determined based on a controlresource set (CORESET) group identifier configured to each cell or not.15. The terminal of claim 14, wherein in case that the number of cellsassociated with the capability to monitor PDCCH candidates is equal toor less than the number of configured cells, the maximum number of PDCCHcandidates for a cell is determined as a preconfigured maximum number ofmonitored PDCCH candidates corresponding to a subcarrier spacing of thecell or a multiple of the preconfigured maximum number of monitoredPDCCH candidates corresponding to a subcarrier spacing of the cell basedon the CORESET group identifier configured to the cell.
 16. The terminalof claim 14, wherein in case that the number of cells associated withthe capability to monitor PDCCH candidates is not equal to or less thanthe number of configured cells, the maximum number of PDCCH candidatesfor a cell is determined based on a number M^(total,μ) corresponding tofollowing equation:M ^(total,μ) =└N ^(cap) ×M ^(μ) ×N ^(μ) /N ^(total)┘, where N^(cap) isthe number of cells associated with the capability to monitor PDCCHcandidates, M^(μ) is a preconfigured maximum number of monitored PDCCHcandidates corresponding to a subcarrier spacing of the cell μ, N^(μ) isa number of at least one configured cells corresponding to thesubcarrier spacing of the cell μ determined based on the CORESET groupidentifier configured to the cell, and N^(total) is the number ofconfigured cells.
 17. The terminal of claim 13, wherein the coefficientis associated with a CORESET group identifier configured to each of thecell in the second set.
 18. The terminal of claim 17, wherein toidentify the search spaces, the controller is further configured toselect a search space to monitor which corresponds to CORESETs of afirst CORESET group identifier (ID) in case that it is needed to selectthe search space to monitor in a primary cell.
 19. A base station in acommunication system, the base station comprising: a transceiver; and acontroller coupled with the transceiver and configured to: identify anumber of cells associated with a capability to monitor physicaldownlink control channel (PDCCH) candidates of a terminal based on anumber of cells in a first set and a product of cells in a second setand a coefficient, determine a maximum number of PDCCH candidates foreach cell based on the number of cells associated with the capability tomonitor PDCCH candidates, identify search spaces to be monitored by theterminal based on the maximum number of PDCCH candidates, and transmitdownlink control information on the identified search space of a PDCCH.20. The base station of claim 19, wherein the maximum number of PDCCHcandidates is determined based on whether the number of cells associatedwith the capability to monitor PDCCH candidates is equal to or less thana number of configured cells which is determined based on a controlresource set (CORESET) group identifier configured to each cell or not.21. The base station of claim 20, wherein in case that the number ofcells associated with the capability to monitor PDCCH candidates isequal to or less than the number of configured cells, the maximum numberof PDCCH candidates for a cell is determined as a preconfigured maximumnumber of monitored PDCCH candidates corresponding to a subcarrierspacing of the cell or a multiple of the preconfigured maximum number ofmonitored PDCCH candidates corresponding to a subcarrier spacing of thecell based on the CORESET group identifier configured to the cell. 22.The base station of claim 20, wherein in case that the number of cellsassociated with the capability to monitor PDCCH candidates is not equalto or less than the number of configured cells, the maximum number ofPDCCH candidates for a cell is determined based on a number M^(total,μ)corresponding to following equation:M ^(total,μ) =└N ^(cap) ×M ^(μ) ×N ^(μ) /N ^(total)┘, where N^(cap) isthe number of cells associated with the capability to monitor PDCCHcandidates, M^(μ) is a preconfigured maximum number of monitored PDCCHcandidates corresponding to a subcarrier spacing of the cell μ, N^(μ) isa number of at least one configured cells corresponding to thesubcarrier spacing of the cell μ determined based on the CORESET groupidentifier configured to the cell, and N^(total) is the number ofconfigured cells.
 23. The base station of claim 19, wherein thecoefficient is associated with a CORESET group identifier configured toeach of the cell in the second set.
 24. The base station of claim 23,wherein to identify the search spaces, the controller is furtherconfigured to select a search space to be monitored which corresponds toCORESETs of a first CORESET group identifier (ID) in case that it isneeded to select the search space to monitor in a primary cell.